It is said that there is a Superman or a Superman reference in every Seinfeld episode. For sure you can catch a glimpse of Superman on Jerry's refrigerator or over by where his stereo is. Also some of the conversations are geared towards Superman. For instance, one episode George and Jerry argue is the Man of Steel has super human humor. They can't figure out if along with super speed, super strength, and whatever else he possesses if he should have super humor.