Who is Kramer?
Cosmo was known only as “Kramer” for many years on the sitcom; not even Jerry knew his real first name. It was George Costanza who found out his unusual name through an encounter with Kramer’s mother, Babs Kramer, in Season Six. Cosmo appeared in all but two episodes: Season Two’s “The Chinese Restaurant” and Season Three’s “The Pen”.
Kramer’s character is based on the real-life Kenny Kramer, a neighbor of co-creator Larry David. At the time of the shooting of “The Seinfeld Chronicles”, Kenny Kramer had not yet authorized the use of his name, and so Kramer’s character is known as “Kessler”.