The couch gag is a running visual joke in the opening credits of the animated television series The Simpsons. The couch gag changes from episode to episode, and usually features the Simpson family's living room couch. A typical gag features the Simpson family running into the living room, only to find some abnormality with the couch; be it a bizarre and unexpected occupant, an odd placement of the couch, such as the ceiling, or any number of other situations. In more recent seasons, the couch gags have tended to be more outlandish and absurd. (...)
One of the longer couch gags to date is "The Ziff Who Came to Dinner"'s 45-second spoof of the short film Powers of Ten. After the family runs in and sits on the couch, the camera pulls up through the roof and continues pulling back - past Springfield, the United States, Earth, the Solar System, Kang and Kodos outside their broken spaceship, and finally the entire Milky Way galaxy. As the scene continues receding, the galaxies turn into atoms, which become molecules, which become strands of DNA, which become skin cells, which become Homer's head. Homer then says "woooow" (later changed to "cool" in subsequent airings.) The early part of the sequence is accompanied by Strauss' Also sprach Zarathustra on the music track, until Kang and Kodos are encountered, followed by a generally eerie and suspenseful underscoring until Homer's scalp is finally revealed.