Smarter Than the Average Dog / CatDog Doesn't Live Here Anymore

S1 E20: Frustrated Cat buys Dog educational videos to smarten him up. But Dog watches them over and over again on fast forward, and  Dog's brain swells to enormous size.  Dog's brilliance comes at the expense of Cat, who's brain cells are being pilfered by Dog. The moronic Cat accidentally blasts CatDog into space in Dog's new  homemade rocket.  Humiliated, Cat and Dog fight over the brain. Their struggle eventually return them back to normal, but now Cat and Dog are faced with the daunting task of piloting their flying contraption back to earth.Winslow wakes up one morning to find CatDog gone.  Winslow throws a Good Riddance, CatDog party with the Greaser Dogs, Squirrel, and Gopher.  After reminiscing about all the good times they had harassing CatDog, the revelers all blame each other for driving CatDog away.