Even as Phil and Keely decide to become a couple, Phil gets the grim realization that the time machine is fixed. It also revealed that Lloyd was intentionally not repairing the time machine because the whole family is so happy living in this century. Upset that Phil's leaving just as they've admitted they love each other, Keely decides not to be there when the Diffys leave. But she changes her mind and rushes to the time machine... too late. Phil begs his father to go back, so he can truly say goodbye to Keely. Keely is reading the school news when Phil comes back to say goodbye. Phil exclaims "I didn't wanna leave without saying goodbye for real," and gives her a big passionate kiss on the lips in front of the entire school. Keely tells Phil to wait for her and Phil agrees and she gives him one more kiss. Phil leaves and goes back to the time machine, only to realize that they have left their pet caveman Curtis in the present, and start to go back. In the final scene of the series, we see Curtis getting food from the fridge. Curtis notices he's alone and panics.