The basis of the talking stomach was writer Spike Feresten's real life experience of imagining his girlfriend's buttocks talking to him while she slept. When recounting the story idea to the other Seinfeld writers the buttocks' "voice" became an inside joke. He told his girlfriend this, and her reaction was similar to Claire's (Sarah Peterson) in the episode. Jerry Seinfeld decided to change the talking buttocks to a talking belly button so that it wouldn't appear to be simple "body humor." Jerry later admitted he wished they'd kept it as the buttocks.
Near the end Kramer has the idea to mix ketchup and mustard in one bottle, which sounded absurd at the time. A few years later such a product became a reality.
George (Jason Alexander) asks his boss, Mr. Thomassoulo (Gordon Jump) if he's heard of The Incredible Hulk. Jump appeared in a 1978 episode of the Incredible Hulk TV series.
Rejected titles for this episode were "The Backslide" and "The Bladder System."