Keely wants to improve ratings for her investigative news show, so she turns to Pim for advice on how to pique students' interest. Pim's tips work, but Phil worries that Keely is sacrificing too much to become popular.
Phil and his family become local celebrities when it's revealed the Diffys are visitors from the year 2121. While fame has some nifty perks, it cannot repair the rift that develops between Phil and Keely soon after he's thrust into the spotlight.
Phil's friend Andy (Orlando Brown) arrives from the future and offers to take the Diffy family back home in his time machine, but only on one condition: Phil must help take part in a mean prank on the town mayor.
Pim resorts to dirty tactics to win the title of “Principal for a Day” against her opposition, Vice Principal Hackett. It comes as no great surprise that power goes straight to Pim's head, forcing Phil and Keely to come up with a plan to remove her from office.
Phil and Keely, who have volunteered to babysit a little troublemaker, use one of the Diffy's gizmos from the future in hopes of improving the child's behavior, but (of course) things don't go as planned. Meanwhile, Pim's latest money-making scheme involves selling homework.
Curtis accompanies Phil on his class trip to a museum, during which they come across a missing piece to the time machine amid a prehistoric exhibit; and the new substitute teacher, Ms. Mip, presents a huge challenge for Pim.
Lloyd's latest idea to get his family back to the year 2121 involves writing his future self a letter for Phil to put in a time capsule at school. The only downside to this plan---if it works---is that all memories of Phil's friendship with Keely will be erased. Meanwhile, Pim makes money raising funds for a not-so-sick rat. Ben Savage appears as himself. Vice Principal Hackett: J.P. Manoux.
The Diffys invite their new next-door neighbor, Vice Principal Hackett (J.P. Manoux), to their home for an average 21st-century supper. Unfortunately, just as Mr. Hackett arrives, Phil's parents get sucked into a vortex caused by the Time Crumpler, leaving Phil and Pim with the unenviable task of entertaining their overly suspicious dinner guest.
Phil and Keely fear that the failing grades that they received on their history tests will detrimentally impact their lives; and Pim sneaks into an R-rated movie with help from an oblivious Curtis. Samantha: Anneliese van der Pol. Sally: Kyla Pratt. Susie: Fran De La Rose.
Phil wonders if he has fallen in love when he becomes jealous of a cute waiter named Robby (Dossett March) who flirts with Keely at the mall; Pim is determined to join a clique cooler than the “fashion zombies” after not getting invited to Candida's slumber party.
Phil and Pim's constant bickering leads their parents to try a technique called “Versa Day”: the two Diffy kids switch bodies to see things from another perspective. While Pim decides to make the most out of the situation by embarrassing her older brother, Phil takes up for his little sis after an encounter with some mean girls at school. In other happenings, Lloyd tries to get Curtis a job.