Phil and Keely pretend to be in cheerleading to impress Mrs. Teslow. Pim tries to find the one thing that Debbie can't stand.
Phil and Keely go to the Tomato Ranch. But Phil is worried about going in the tomato mashing tub as he only has 4 toes.
Phil tries to dissuade another girl's affections; Pim joins the orchestra to sabotage Debbie's solo; Pim meets Bradley Benjamin Farmer.
Phil and Keely enter a science fair featuring next Century's "milk engine" sending Lloyd into a state of panic that the Diffys will be discovered. Phil and Keely sneak into the fair to retrieve the evidence so the Diffys can remain in Pickford.
A school video project causes Phil to overlook his friends' feelings; Pim is recruited for a track meet.
A boy named Tanner asks Keely out, but Phil doesn't really like him. One day when Phil is doing a skit on stage a girl named Darcy walks in and asks the teacher that if he sees Tanner to tell him that she stopped by. Phil thinks this is kind of weird, so, using his Instamorph, he changes into Tanner and goes to investigate. He finds out that Darcy is also Tanner's girlfriend and that he is two-timing Keely, but when he tells her she just gets mad at him. Later, while Keely and Tanner are doing a skit on stage Darcy walks in and kisses Tanner right in front of Keely! Meanwhile, Pim tries to get Debbie and Bradley to break-up.
Lloyd and Barbara decide to go on a weekend road trip for their anniversery. They leave Phil in charge of Pim and if everything goes right then Phil will get an afterburner for his skyak. Once Pim hears this she is not happy and tries everything in her power to make the weekend go bad so Phil won't get the afterburner.
Phil and Pim worry that Lloyd will embarrass them when he plans to play American folk music at their school concert; Barbara takes Curtis to a dentist when he gets a toothache.
Phil and Keely start a day-care service for dogs to earn money for concert tickets. Phil uses a futuristic gadget to understand what a dog is saying.
Phil is sent to second grade to work on his writing after he messes up on his cue cards for the news. Pim cheats on a test and her conscience bothers her.
Debbie enlists everyone is school to help her bake cupcakes except Pim. But soon enough Pim is forced into giving the drum beat to the bakers. Phil and Keely try to help the helpless bakers.
Phil gets detention and goes to the dance with his new "guy friends." But when a bull attacks his new friend, he morphs it into a cat. Pim is tardy too many times, so she dresses Curtis up as her father to get off being punished.
Phil tries to impress the mayor's daughter but things get bad when he switches places with Curtis. Pim realizes that she can't stand Debbie and doesn't even want to be her friend.
Phil and Keely are on a virtu-date and the robot waiter starts flirting with Keely and Phil is jealous.
Phil and Pim have been fighting all week. Lloyd and Barbara couldn't take it any longer so he called for a Versa Day. For one school day Phil and Pim have to switch lives. Meanwhile Lloyd wants to get Curtis a job....if only he could find a place that will hire him.
Mr. Hackett moves in next door and the Diffys invite him for dinner. Pim tries to sell the house.
Phil and Keely have a huge test in Mr. Messerschmitt's class, but take advantage of The Giggle. Phil and Keely, then, both fail the test. So Phil tries to make it up to Keely. Meanwhile, Pim goes to an R-rated movie and brings curtis as her parent.
Phil replaces Curtis as field trip chaperone when Mr. Hackett is too ill to escort their class to the museum. Phil locates a part from the time machine during a class trip to the museum.
When Tia moves away, Keely gets Phil into doing everything that she would normally do. So Phil hooks Keely up with the new girl.
Keely finally gets the courage to ask Phil to the dance. Phil agrees to go and Keely walks away as students file past. The students clear and both Keely and Phil see the other doing a happy dance. Later, Phil's dad, Lloyd, tells the family that he has fixed the time machine and they are leaving the next day. Phil has to break his date to a crushed Keely. After Phil tells Keely he is leaving Lloyd breaks the time machine. Phil tells Keely he can now go to the dance with her but she already has another date, Owen. Phil is crushed and asks Via to the dance. At the dance Via and Owen help get Phil and Keely together.
Mr. Messerschmitt insists his students take the Career Placement Test. However, Phil doesn't know what he wants to do and doesn't want to be trapped in a job for which is not suited.
It's Keely's birthday and Phil wants to give her the best birthday she has ever had. Last year he had forgotten her birthday so he wanted to go all out with her present this year. Phil's plans for the perfect outing are crushed when Lloyd takes out all the batteries to the future gadgets because it will get him "one step closer to fixing the time machine". Meanwhile Pim meets a fellow prankster and even has a crush on him.
Lloyd realizes that Pickford High School's time capsule is the key to returning the Diffy's to the future, he tells Phil to warn them from taking their time travel vaction in the year 2121.
When Phil & Keely baby-sit Nathan, the trouble-making nephew of Mr. Messerschmitt, they get more than they bargained for, so they use the New-Ager, a device that changes one's behavior. But things go hay-wire, leaving Nathan to act like an old man, while Phil is acting like a little boy. Now it's up to Keely to solve the problem before Mr. Messerschmitt and Phil's dad get home. But her only salvation, Pim, is too busy using the Wizrd to create and then sell the latest school project.
The Diffy's catch a futuristic disease called greenemia which causes them to turn green and act completely opposite to how they usually act.
Phil uses future knowledge to solve one of Mr. Hackett's seemingly impossible math problems, but Keely inadvertently blurts out the answer and is promptly upgraded to advanced math class. Rather than have Mr. Hackett even more suspicious of his family, Phil helps Keely continue to look smart among the other genius students - while Keely teaches her new classmates to navigate the shopping mall. After Candida pulls a static electricity trick on her, Pim shuffles her way to find the best method for acquiring energy.
Keely tries to get together two people and it backfires on Phil. Pim becomes a "psychic" and fools Mr. Hackett.
Phil loses the wizard and to his suprise he finds that Mr. Hackett has it. Now Phil is on a mission to get the wizard back. Will Mr. Hackett find out Phil is from the future?
Pim abuses her power when she becomes principal for the day.
Phil makes a fool out of himself when he gets a question wrong in history and everyone laughs at him. It seems in the future they cloned Abraham Lincoln and Phil forgetting that he was in the present answered that Lincoln went down known as Stinkin Lincoln. Phil is angered by coming up with another excuse for why he said what he said. He feels like he is going to burst so he tells everyone his secret.
When no one watches Keely's investigative reports show Pim comes to the resuce by offering to help make her popular amongst her viewers again but Keely realizes that Pim is just abusing her to make money and goes back to making "real news" with Phil.
Phil is growing tired of everyone going into his room without his permission. He wants privacy and he isn't getting that from his room. When Lloyd stores tools from the Time Machine in Phil's room that shouldn't be next to each other, it ends up blowing the floor out and Phil has to live somewhere else. He chooses the garage and shares it with Curtis. But when Curtis is sick of Phil he decides to fix Phil's room and live there instead.
Phil unwittingly prevents his great great grandfather from meeting his great great grandmother, thus causing a chain reaction in which he and his family are erased from existence.
Phil and Keely finally become a couple. Though Lloyd has all of a sudden fixed the time machine, now it's time for the Diffys to head back home. It's Keely's worst nightmare when she realizes Phil is leaving for real.