In which episode(s) of "Seinfeld" did Kramer not appear?

Kramer appeared in all but two episodes: "The Chinese Restaurant" and "The Pen", in the second and third seasons, respectively.

https://en.wikipedia.org/wiki/Cosmo_Kramer

The Pen is the only episode of Seinfeld in which neither Kramer nor George make an appearance. (Kramer also does not appear in the Season 2 episode, "The Chinese Restaurant".) Jason Alexander confessed in the DVD extras that he walked up to Larry David and told him he would quit if he was ever written out of the story line again. This was the second-to-last episode not to feature all four main characters. (Elaine Benes was not seen in Season 4's "The Trip")

https://en.wikipedia.org/wiki/The_Pen