When the Diffys find a caveman who stowed away in their time machine, they agree to make him a part of the family. But after Curtis attacks Mr Hackett at school, Lloyd decides he must go.

Phil bunks off the family's annual Unification Day celebration to attend a cool 11th grade party with Seth, Keely and Tia.

Phil uses the `insta morph' to duplicate the image of Tanner, Keely's new found crush, to learn the truth behind his two-timing ways. Pim's plan to break up Debbie Berwick and Bradley backfires when Bradley instead falls for Pim instead.

Sibling rivalry comes into play when Phil and Pim are left home alone and Phil is in charge. In an effort to prevent Phil from receiving the afterburners he longs for if things run smoothly, Pim runs away on the skyak. After crashing, Phil rescues her from a cliff and Pim realizes how much he cares.

Phil comes to Pim's aide when he learns she is being bullied, only to encounter the bully's older brother Myron - an even bigger bully! With the use of their futuristic Invisi Spray, Phil and Pim overcome their troubles. Meanwhile Lloyd is busy trying to replace Mandy Teslow's lawn ornaments that Curtis decided to bring home.

Phil's poor penmanship lands him back in Miss Winston's second grade class. Tanner shows him up in front of the whole school, but Phil learns to laugh at himself.