Conversation so far:
Who is Cosmo Kramer based on?
The character of Kramer was originally based on the real-life Kenny Kramer, a neighbor of co-creator Larry David from New York.
Why did co-creator Larry David use Kenny Kramer to base the character of Cosmo Kramer on?
Was Kenny Kramer a friend of co-creator Larry David's?

Question: How were relations between the two?
Self-contained rewrite: How were relations between co-creator Larry David and Kenny Kramer?