Ned goes with his dad on Take Your Child to Workday, and while he initially thinks his dad's job is dull, he eventually thinks that his dad is a government spy, and tries to find out more information.

When Ned complains that he can't go to summer camp, Newton mistakenly thinks he's describing boot camp. He signs Ned up for the army, and while no one notices that he's 10 years old and insists he does basic training, Newton tries to find a way to get him out.

Ned decides to climb a small hill to raise money for charity, but Newton thinks he would raise more if he climbed Mount Everest, so he takes Ned there and helps him climb it.

Winter is coming, and Newton learns that newts hibernate during the winter, a process he doesn't want to go through. When he learns that birds migrate instead, he decides to go away for the winter and takes Ned along.

Ned and his family are all set to spend a weekend in exciting Gamble City, but when Ned's mother finds out there's gambling there, she decides to have Ned stay with his aunt and uncle instead, who is a depressed, puritanical Eastern European couple who think fun is unhealthy. As Ned and Newton become more and more bored, Newton decides to have the whole house shipped to Gamble City.

Ned was born on New Year's Day, and as such, is expected to play Baby New Year every year at a New Year's Eve pageant. He doesn't want to do it at his age, so he desperately tries to find out if another New Year's Baby has been born in the town, saving him the embarrassment.

Ned's been given a small role in a horror film "Car-Driving Trees of Egstappa Part 2", but soon finds out that the Car-Driving Trees are real, and plan to wipe out Friendly Falls.

Friendly Falls is experiencing a drought, which is ruining Ned's summer, and might cause trouble for the various newts in town when the ponds and rivers they live in dry up. Newton tries to end the drought with various plans to make it rain, and they succeed, even though it has been raining so much the town flooded.

Ned gets a mild concussion, but eventually gets to play outside. It goes horribly awry when Ned is sent to the hospital thanks to one of Newton's forms calling the ambulance, even though he's actually feeling fine. Following this, Newton (in his form when not shapeshifting) takes it on his own to bring Ned back to health.

Ned and his friends are collecting 10,000 bags of pet hair for charity, but Ned's cousin Renfrew wants to sabotage their efforts. Newton will have none of it, so he attempts to get Renfrew off their case.

The Friendly Falls Future Fair has been reopened after it was closed in 1964, which makes Ned excited. The lineup to get into the fair is huge, though, so Newton sneaks him in so they can see the exhibits. Ned is dismayed to see that they haven't been updated since 1964, and most of the displays are ridiculous: there's a car with a record player mounted on the dashboard for a "car stereo system", a kitchen where malfunctioning robots cook food, and even robotic pets (much to Newton's shock). He goes back to his parents just as they get to the front of the line, and says he doesn't want to visit the Fair anymore.

Ned comes with his parents on their anniversary cruise, but thanks to Newton, he ends up on the wrong boat.

At Ned's family picnic, Newton develops amnesia, and thinks he is one of Ned's obnoxious uncles.

Ned visits his grandparents, who are retired farmers. Newton, who doesn't know what retirement is, thinks the animals and crops are simply being lazy and tries to whip them into shape.

Ned's mother goes to a different town to participate in a perfume saleswoman convention, but Ned mistakenly thinks that they are moving to this town. To convince Ned's parents that they shouldn't move there, Newton poses as a tour guide to describe various "horrors" throughout the town, and tries to make it seem as though wild boars roam the streets by putting boar masks on the stray dogs.

Ned's teacher has developed a new alphabetical desk arrangement, which unfortunately puts Ned in the back of the class, and Linda Bliss at the front. Because he wants to be able to sit right behind her, Ned and Newton arrange various schemes to make sure the few kids in between Ned and Linda get taken out of class, either by moving, being transferred, or having their last names changed. But at the end, when it looks like Ned and Linda get to sit with each other, Ned's teacher grabs him away from Linda and introduces to him two pairs of identical twins named Jenny, Kenny, Penny, and Lenny, who are told to sit between Ned and Linda, much to his disappointment.

Ned is made to play with his obnoxious rich cousin, Norman, who has a female pet newt. When Ned feeds both Newton and the other newt Zippo food, they both change, and Norman's newt wants revenge on Norman for constantly neglecting him. Newton falls for the female newt, whom he names Buttercup, and Norman is terrified by the two giant creatures that have suddenly appeared.

While Ned is working at a TV station, Newton accidentally destroys all of the station's pre-recorded content for the weekend, and he and Ned have to record all-new footage to replace it. They re-enact the news, several TV shows, and try to splice in whatever spare footage they can find to fill time.

When Ned's parents hear him talking about Newton, they assume this is a new imaginary friend, similar to one Ned had in his early childhood, a big talking red shoe named Shoe. They take Ned to see a child psychiatrist, but when they accidentally see Newton who has been going out and around in the form of a shoe since he found out about Shoe, and assume that Ned's imaginary friend is visible to them as well, they also go and see a psychiatrist. In the end, it turns out Shoe is real.

Ned notices that his alphabet soup is missing the letters N, E, and D. Curious as to why, he goes to the company that makes the soup, which turns out to be the same one that makes the Zippo Newt Food, to find out what's going on.

Ned has a cold, and Newton shrinks himself down so he can enter Ned's body and cure him.

With Mother's Day approaching, Newton thinks the purpose of the holiday is to give your mother as a gift. He finds his mother and proceeds to give her to Ned.

Ned's parents were planning a trip to New York City but had to cancel it when they heard, from Doogle's parents, that they've been watching a show about the urban legend that alligators live in the sewers. Ned and Newton go there to prove that the rumor is false, mainly trying to "blend in with the locals". But they end up falling into the sewers when they're ready to give up, and also accidentally find the sewer alligators.

Instead of a lemonade stand, Newton convinces Ned to instead start as a private detective service. Linda hires him to find her missing earring, and Doogle hires him to find his missing dog, Lummox. Ned eventually finds out that Lummox was accidentally made into a professional baseball pitcher, and then tries to find a way to get him out of the Major Leagues.

Ned had rescued an endangered plant for a science fair entry, but the plant soon starts to grow too much and threatens to take over the world.

Newton helps Ned and Linda win tickets to a rock concert, but their date is ruined when Doogle, while digging a hole to raise money for charity, accidentally unearths a race of subterranean trolls bent on taking over the world's "metropolises-es", and Ned and Newton have to stop them.

Ned goes to the pet store, hoping to buy an elephant, but all he can afford is a listless newt he called "Newton" who does nothing but sit in a fishbowl. The pet store owner sells him a can of Zippo For Newt, which turns Newton into a 6-foot transforming anthropomorphic newt. Ned and his new pal, Newton, trash the house by playing Tag.

Ned has a crush on the girl across the street, Linda Bliss, but can't talk to her. Newton tries to get her attention by throwing a tiny pebble against Linda's bedroom window while she's asleep, but ends up throwing a boulder, and destroys the window. Ned and Newton desperately try to replace it before Linda wakes up the next morning.

Ned's class are making small floats for the annual Friendly Day Parade, and Newton wants to help. He ends up making an enormous, barge-sized float for Ned and ruins the parade when the float causes massive property damage and sinks in the lake.

Ned's tattletale cousin Renfrew comes to visit. He destroys most of Ned's toys and repeatedly tells on Ned. Newton decides to drive Renfrew away by causing a series of ridiculous situations, which causes Renfrew to have a nervous breakdown as he tattles to Ned's parents about them.

Ned's father gives Ned a vintage "Captain Ocelot" action figure after his son takes an interest in the show. Ned's mother, however, throws it out, and Ned and Newton have to go to the Friendly Falls Dump to find it again. Afterward, they find out that the dump owner is actually the retired actor who played Captain Ocelot.

Ned's mother wants a 35 carat "Goldina" ring for her birthday, but Newton just insists it's a "cheap replica" of a sacrifice ring used by a group of Peruvian savages called the "Jajamojos". Ned and Newton go to Peru to get the ring, and brave the dangers of a temple full of booby traps, and escape being thrown in a volcano.

Ned is sent to the grocery store to get a can of tomato paste, but Newton instead suggests they go to Mars, thinking that it's made of tomato paste similar to the idea that the Moon is made of green cheese. They go to Mars, and it is made of tomato paste! But they find that the tomato paste there tastes awful, so they decide to just get it from the grocery store after all.

Ned wants to impress Linda at the school dance, but the town showoff, Rusty McCabe, also wants to impress Linda, and challenges Ned to a dance contest. Ned is completely unable to dance, but he hopes that Newton will be able to tutor him. When this doesn't work, Newton gets the idea to put Ned in a large costume, where he stands on his shoulders while Newton dances.

Ned starts a paper route to save up money for a bike, but Newton has more ambitious plans for him. He turns Ned's paper route into a media empire, making him extremely wealthy, but depressed because he doesn't even have time to ride his new bike.

Ned and Linda go on a date to the circus, after Newton accidentally sells Ned's parents' car to raise the $5 ticket price. The circus turns out to be a scam with the circus acts being subpar. However, to prevent the date from being a failure, Newton saves the circus by performing a series of astounding circus acts but also ends up causing the circus animals to stampede through town.

After a fun weekend, Ned says he can't wait for the next one. This gives Newton the idea to build a time machine out of household items so that they can go back to Friday and do the weekend over again. They can't control the machine, however, and it ends up taking them to the Jurassic period, where Ned accidentally stomps on a fly and changes history, causing newts to be the dominant life form on Earth instead of humans. They go back and fix this change, but still have trouble controlling the time machine to take them home, causing them to end up at Gilligan's Island. However, it turns out to be a dream, but the trip to Gilligan's Island was proven to be real.

Ned attends Boy Scout camp, and Newton notices that the other scouts have more merit badges than Ned. Ned doesn't care, as he's allergic to the outdoors and doesn't enjoy being a Boy Scout, but not wanting to see his owner disgraced, he motivates Ned to earn as many merit badges as he can. Eventually, when Ned becomes the most decorated Boy Scout, Newton decides to wrap the entire forest in anti-allergenic plastic, but when he does, Ned finds out that he wasn't allergic to anything in the forest, but to his mother's macadamia-nut cookies that she always packs him.

The company that manufactures Zippo Newt Food has changed the formula, which leaves Newton unable to control his morphing ability. Ned and Newton go to the corporate headquarters to complain, but the president of the company refuses to go back to the old formula until Newton demonstrates that the "new formula" causes newts to grow six feet tall and change into different forms.

In another attempt to get closer to Linda, Ned plans to audition for a school production of "Little Red Riding Hood". Newton, eager to help out, wants to be cast as the Big Bad Wolf. Unfortunately, the new school drama teacher is an ex-Hollywood executive who makes Ned and Newton repeatedly change the play until it's a post-apocalyptic science fiction story called "Mad Max and the Chicken-Wolf", where Linda isn't even in it.

Ned has been watching too many monster movies, and when he's left in the house alone, he's paranoid that there are monsters around the house. This isn't helped when his parents ask Uncle Frank and several friends of his to check on him, and they're all dressed as monsters, on his way to a costume party. Newton, after thinking about what killed all the monsters in the movies, decides to let the monsters fall to their death by jacking up the house and pushing them out the door.

Ned's father opened a new bank account for Ned, after finding all the change around Ned's room. To Ned's horror, however, that means he has deposited his "lucky penny", a treasured penny that has an image of Gene Hackman as Lex Luthor on it. When the bank refuses to get it for him, Newton helps Ned by breaking into the bank vault to find it. They do, but Newton had to give away $3.5 million in the bank vault to make it easier to find. They're saved, however, when a passing coin collector points out that Ned's penny is only one of two in the entire world, worth $3.5 million. Ned and Newton quickly put all the money back in the vault, and the bank owner gives Ned the only other Gene Hackman penny in existence.

After watching too much television, Newton gets the idea to improve Ned's life with all the things featured in the various commercials he's watched.

Ned's family is on a long, boring car trip, with only a "Vehicle Bingo" game to pass the time. Ned's parents accidentally leave him at a rest stop, however, and Ned needs Newton's help to catch up to them. After being blasted off to Russia, they end up traveling around the world and take every mode of transportation on the Bingo card trying to get back, which perplexes Ned's parents.

Local hero Gus Gingrich has held the world's record for "Most Pants Worn at Once" since 1959, until a man in Germany breaks his record, leaving the town heartbroken. Ned and Newton decide to restore the town's spirit by trying to break a record, but Ned fails at each record he tries. Because of this, however, Ned breaks the world record for "Failing at a World Record" (according to Newton) and restores the town's spirit.

Ned is on a dull field trip at the Friendly Falls Museum of Dusty Old Things, and has to fill out a worksheet of questions about the historical exhibits in the museum. Newton wants to help, but many of the answers he gives are wrong and absurd, such as how Archimedes discovered the bathrobe, and how the Great Wall of China was a backyard fence built by one laborer who couldn't build corners. Ned finds out too late that all the answers are wrong, but Rusty McCabe forces him to trade his worksheet with him, assuming that Ned's answers will be better.

Rusty McCabe has built a secret clubhouse that he won't let Ned in, so in response, he makes his own secret club in a tree fort. Newton wants to help, though, so they end up building an enormous, five-star clubhouse in the tree, and it becomes the most popular club in town. Rusty begs to be let in, but when Ned lets him in, he accidentally causes the clubhouse to collapse.

Ned's friend Doogle has a pet dog, an obese, listless dog named Lummox. Doogle, when overhearing his parents talking about fleas on Lummox's fur, thinks his parents are going to get rid of him, and feeling sympathy for the fellow pet, Newton tries to prove Lummox's worth by setting up a series of situations where Lummox does incredibly useful things for Doogle's family.

Newton has been acting stranger than usual, and when Ned takes him to see the veterinarian, Newton professes that he has fallen in love with her. As the day goes on, however, he keeps falling in love with dozens of other things, such as a passing roller skater, many different zoo animals, and mostly an ice cube tray. Ned eventually finds out that he's only acting this way because he's shedding his skin.

Ned has been entered into a track and field day at school, but he's not happy about it, since Rusty McCabe always wins every event. He wins so often, he's even gotten his own theme music, with Yo-Yo Ma as a guest cellist. Newton thinks Ned into every single event at the track day, including team sports. Although by the end, Rusty has won everything and Ned is exhausted, he's given a special award for being the first person to participate in every single event.

Ned's parents have the flu, and want Ned to do the day's chores. Newton tries to help, to get them done faster, but he ends up being incredibly destructive.

The local mall is holding a contest where the first person to guess how many jellybeans are in a jar will win a drivable toy car. Ned wants the car, but when Newton comes out, he wreaks havoc around the mall and causes him and Ned to be locked inside after it closes. The sadistic mall security guard wants to ban them from the mall, but they're able to blackmail him when they find out that he's been counting the jellybeans in the jar, one by one, to win the toy car. To keep them quiet, the mall cop gives them the car.