Peri wants to know what he's good at. After running from Two-Legs Joe, Peri and Entrèe find a secret room for bowling, Peri realizes that he was born to bowl. However, in trying to prove his bowling ball can be used for other activities, Peri is frustrated by the results and throws the ball into the volcano. After this, an alien civilization, the Pinnians decide to take over the island and treat the mutants like slaves. By realising these aliens have a kinship with bowling, Peri decides to confront them doing what he does best.
In search of fun in the lab, Peri and Entrèe find one of the doctor's journals, which supposedly tells what the purpose of Peri is. The friends go to visit Mister Smarty Smarts hoping he can read Peri's purpose to them, but it turns out he can't read. He lies and says Peri was created to be the best friend of Entrèe. Peri, excited at discovering his purpose, becomes obsessed with Entrèe, who can not bear being constantly chased by Peri. To teach Peri a lesson about personal space Entrèe decides to splice them together.
Peri and Entrèe are looking for someone to join them in a game of Bucket-Stick-Fruit-Ball, but nobody wants to play. The terrifying Princess Pony Ape Hands is the only one who wants to play. However, she plays too rough so Peri and Entrèe quickly try to ditch her. Princess throws a major temper tantrum and decides to smash the old nuclear reactor.
When Peri finds out he has small cratures living in his fur, he wants to keep them so they can have a little society there, but when he begins to stink, everybody wants to clean him.
Mister Smarty Smarts, tired of the incompetence and ineptitude of the inhabitants of the island, creates a device to make everyone smarter. His utopia is soon ruined when everyone's intelligence goes way past his. After being treated like an idiot, Smarts decides to make everyone unintelligent again.
After escaping Princess Pony's tickle attack, Peri and Entrèe find an old golf cart. Entrèe repairs the vehicle, replacing the engine with the brain of an evil robot. After naming it Gordon, Peri and Entrèe travel around the island with their new car. After a few days of driving, Peri and Entrèe don't want to drive again for a while. After they abandon Gordon in the jungle, he decides to cause trouble.
After Peri and Entrèe accidentally shoot themselves into the sky with one of Fuzzy's transportations, Entrèe uses his chicken wings to stop him and Peri falling to their death. However, he crashes through a building and loses control. After they crash through a makeup store, a clothesline and a wig shop (completely changing their appearance) they land in the tree house of Princess Pony, who believes they are magical fairies. After learning she'll give them everything they ask for in return for dances or fairy tales, Entrèe decides to use Princess to get everything he wants.
Peri and Entrèe find a mustachioed Entrèe-like being frozen in a block of ice. The two friends thaw him out and learn that his name is Apéritif. Apéritif introduces himself to Entrèe's "delicious" friends, who all admire him more than Entrèe. Entrèe, thinking he is nothing compared to his brother, decides to freeze himself, but soon discovers that Apéritif is not the gentleman everyone thinks he is.
Entrèe is tired of walking, working and moving of any kind and wishes he could just be lazy for the rest of his life. While walking through the jungle he meets Slouch Potato a lazy mutant who teaches Entrèe how to get a chump to do everything for him. After annoying Peri with his laziness, Entrèe is left lying in the middle of town where he starts to grow roots that stick him to the ground.
Peri and Entrèe want to thank Joe for everything he's done for them and the island. After asking Compuhorse what they could do to make him happy, they decide to give him Peri's arms for a day. Joe is pleased but grows too fond of Peri's arms and doesn't want to give them back.
Peri and Entrèe want to know why Patricia is so upset and become "The Smile Squad", trying to cheer her up in outlandish and fruitless ways. When that fails and they make her even more upset, they decide to use a brainscan machine to look into her mind and see what she's thinking. They find out that Patricia feels lonely because she's the only none-mutant on the island. After some thinking, Peri comes up with the perfect plan to make her feel like one of them.
Mister Smarty Smarts decides to use the power of Peri and Entrèe to take control of the island.
At the supermarket, Entrèe has a barcode on his butt scanned, and finds out that he is two days away from his "best before date", after which he will supposedly turn to mush. After a day of trying desperately to "turn back the clock", Entrèe switches places with Peri, pretending that Peri is Entrèe, with only a day to live. Peri, buying the deception, decides to destroy all of "his" stuff, and tells his friends what he really thinks of them, as read in "his" diary. When the time finally comes, Peri realises the truth, and Entrèe, instead of turning to mush, gains a hair-like growth of mould.
When Peri and Entrèe accidentally cause a Whirrel to destroy half the town, Joe loses his temper, demolishing the other half. The other mutants tell Joe that he needs to control his temper. Joe, hurt, leaves, declaring Peri and Entrèe the new mayors. In solitude, Joe hears from the bird on his back, Lord Wingus Eternum, who teaches him how to control his anger. However, when an entire pack of Whirrels attack the town, Joe is forced to regain his temper in order to stop them.
Patricia goes on vacation, reluctantly leaving Peri and Entrèe as housesitters. Peri and Entrèe end up turning the house into an indoor jungle, and when Patricia gets back, she is captured by her pet Molesters, who have turned into a savage tribe by their new environment. Peri and Entrèe mount a rescue attempt, but discover that the Molesters have actually made Patricia their queen.
Entrèe becomes obsessed with getting everyone to like him. An accident with a pair of very tight jeans makes him realise that the milk from his top-right udder, "Nugget", is very tasty. Everyone loves the "Nugget" milk, and Entrèe soon becomes incredibly popular, to the point where he shuns Peri. However, everyone else then becomes addicted to the milk, and when "Nugget" runs dry, they chase after Entrèe.
Entrèe's lucky stone goes missing and Peri is determined to find out who took it.
Compuhorse is boring. At least, that's what Peri and Entrèe think, until they discover his built-in videogame, Cubewhacker.
Peri and the others try to cheer Fuzzy up by making the island look like the long sought goal in Fuzzy's jungle journies.
While Mister Smarty Smarts ponders where he went wrong after another plan ended in defeat, Octocat looks to carry out a plan of her own.
Entrèe makes promises to all his friends to get anything he wants but has no intention to keep the promises he makes. He soon makes one promise he regrets.
After a particulary exhausting day of stomping, Joe wakes up to find out that he can no longer stomp. Peri and Entrèe decide to help Joe find his stomp again, by bringing him to his "happy place". Meanwhile, Smarty Smarts capitalises on Joe's lack of stomping by using his "Cyber-Stomper" machine to terrorise the village.
Peri gains super powers after licking a glowing rock in the lab and Entrèe grows very jealous of him as a result.
Peri starts to move very fast from eating the sugar products received from doing favors for everybody. However, he soon realizes his speed comes with a price.
Peri gets a new pet, Pistachio the buppy. When Pistachio runs away, Peri is heartbroken. After visiting Compuhorse, Peri decides to not feel any emotions anymore, becoming "Compu Peri". His friends decide to try and snap him out of it.
While working on her novel, "Marzipan Meadows and the Kingdom of Adventure", Patricia is constantly distracted by the antics of the other islanders. She quickly loses her temper, threatening to beat everyone up if they don't let her work in peace. When Patricia tries to move on with her story, she experiences writer's block, and realises that her friends crazy antics actually gave her inspiration.
After their friends laugh at them for crying monster, Peri and Entrèe try to make a monster of a cute little mutant called Melvin.
Peri wakes up one day and finds he has turned completely pink but doesn't know how to handle the new look.
Peri and Entrèe find a remote that can control a local volcano. However, their playing with the remote drains the volcano of lava and leads to problems.
Entrèe decides to go on a mayonnaise only diet and this results in him bringing a jar of mayonnaise to life.
While trying to find batteries for a "Mr. Jigglesworth" toy, Peri and Entree find a pair of walkie-talkies, and use them to pull pranks on the other mutants. Soon after, though, Entree starts using his walkie-talkie to ask Peri for help with everything, causing Peri to discard his in anger.
Being chased by Wunny Sharbit, Peri manages to trap him in a glass tube, which he finds out has a translator device that allows Wunny to speak. Putting the translator around Wunny's neck, Peri takes it upon himself to teach Wunny the difference between friends and food.
Entree, desperate for respect, finds a helmet in the Doctor's lab, which teaches him kung fu. Entree is quickly corrupted by his new-found talent, and takes over the entire town, beating up anyone who challenges him. Peri uses the helmet to learn how to make ballon shapes, using this skill to defeat Entree.
After being tormented by Peri and Entree, Smarty Smarts and Joe go to their "happy place", only to find out that it is the same place. Realising that they share a mutual dislike of the annoying duo. The two become friends, pooling their resources to deflect Peri and Entree's antics, and pulling a few pranks of own.
After Entrèe laughs at Fuzzy Snuggums' latest attempt at exploring, Peri tells him that it's Fuzzy's dream. He shows Entrèe that Patricia and Joe have dreams too, but Entrèe scoffs, saying his only dream is to eat something delicious. After eating a pickled egg from the Doctor's fridge, Entrèe passes out. After waking up, he starts to hear a voice in his head telling him to do things.
When Mr Smarty Smart's blames Octocat for all of his mistakes, she leaves and makes Peri her new master.
Entree is bored and decides to have fun on the island. Peri, Joe and Patricia stop him and he accuses them as fun wreckers. The next morning Entree jet-skis the island to Antarctica and the island is attacked by Yetis. Entree sees that Yetis can do whatever they want and decides to join them.
When Peri and Entree decide that they have too many things to do, they use one of the Doctor's old machines to make themselves some clones (Ponie and Underpants) to help them get things done. However, the two clones decide to take over Peri and Entree's lives forever.
While picking on a Whirrel named Ed, Entree and his victim fall off a cliff. The landing causes their brains to pop out and rebound into each others' heads. Entree quickly enjoys his new life as a Whirrel, and the unassuming Peri enjoys Ed's pleasant attitude. Entree is then ordered by a group of Whirrels to kill himself for his crimes against Whirrel-kind.
After a series of bad nightmares, Peri decides to use one of the Doctor's dream machines to enter his subconcious and confront his nightmare monster. However, once inside, he discovers that the toaster-headed monster isn't such a bad guy after all. Together with Entree and Patricia, they become "Dream Gladiators", protecting the dreams of all the mutants on the island.
After experiencing painful itching, Peri becomes a chrysalis, emerging to reveal a beautiful pair of butterfly wings, which entrance anyone who looks at them. Entree takes advantage of this by charging the other mutants food to look at Peri's wings. Mister Smarty Smarts tells Peri that Entree is using him, convinces him to banish Entree, and starts using him for his own nefarious goals.
Sick of the constant abuse Entree heaps upon them, his stomach, heart and brain suddenly jump out of his body, abandoning him. Entree then ingests Peri, having him fulfill the roles of his AWOL organs. After a few false starts, the arrangement becomes satisfactory for both of them. However, Entree's organs return, having outstayed their welcome by annoying everone else on the island.
After a busy day of helping the other mutants, Patricia creates "Mrs. Motherly", a computer system designed to help everyone on the island with everything. Mrs. Motherly's drones go off to help, but they soon start doing everything for the mutants. Tired of this, Patricia, Entree and Peri team up to shut down Mrs. Motherly.
Peri and Entree torment Fuzzy with a pranking game called "Island Fools", causing him to turn into a musclebound brawler, who sees every other mutant as a robot to be smashed. Knowing that only another super-soldier can beat a super-soldier, Joe tries to convince Octocat to fight Fuzzy.
When Peri and Entree fall in love with a pancake, they start to fight each other over it.
After being chased by the Wunny Sharbit, Peri and Entree get stuck up a tree. Entree makes a hanglider out of his chicken wings and promises to come back for Peri. But when a mysterious mutant hangs around town and becomes friends with Entree he forgets about Peri. After some time however, the new guy starts to torture Entree with a game called "you have betrayed me and now I will have my revenge".
Entrèe is very bored and decides a jetpack might cure his boredom.
After Entrèe gets into a fight with a Mole-Ster named Sid, Peri takes care of it. After a number of days Sid leaves. Meanwhile, Mister Smarty Smarts has developed a shrink ray, which he uses to shrink all the town members. Peri and Entrèe decide to ask the Mole-Sters for help.
Entree time travels with Patricia and Peri to find out why Two-Legs Joe doesn't like him.
Peri is feeling under the weather and his refusal to stay in bed lead to problems for everyone around him when his illness worsens.
After Lord Wingus Eturnium convinces Joe to go to the other side of the island (With "Help" from peri and Entree) to meet with his kind, He is given a choice to have Joe separated from himself, but finds that it means having Joe ground off of him.
After Peri discovers that saying 'Poosh' can make Entrèe do anything he wants him to, he works him to exhaustion. When Patricia and Two-Legs Joe find out, they decide to send Peri on a quest for the Blagy Parble to give Entrèe time to rest.