Kramer was based on Kenny Kramer, Larry David’s real-life eccentric neighbor from his days living in Manhattan
When writing the episode, David was hesitant to use Kenny's actual last name. He correctly predicted that if they used the name "Kramer," Kenny would try to exploit the association to the absolute maximum - which he did.
Kenny Kramer immediately capitalized on the show's massive success, launching the real-world "Kramer's Reality Tour" (a New York City bus tour mocking the show's locations) and running for mayor of NYC.