In real life, one of Jerry Seinfeld's first TV appearance was on The Merv Griffin Show in 1981. Seinfeld was just 27 years old.
The "commercial break" music Kramer (Michael Richards) chose for his Merv Griffin set is the same as the theme music of the "Jerry" sitcom pilot from episode 4.23, The Pilot (1993).
Jerry Seinfeld actually appeared on The Merv Griffin Show (1962) in 1986 (Episode dated January 4th).
The scene where Jerry and Kramer talk about Cain and Abel in the beginning was cut in syndication.
"The Merv Griffin Show" ended in 1986, more than a decade before this episode first aired. As its main set had long since been destroyed, the "Seinfeld" production crew made an approximate replica, which took up so much space, part of the set for Jerry's apartment had to be temporarily dismantled to make room.