Like few comics who came before or after his unfortunately short-lived reign, Kaufman was a character day in and day out, from his Taxi work as Latka Gravas to his Tony Clifton persona to his sketch show shenanigans to his real-world stunts and mini-controversies.
Taking on a role like Kramer would have presumably been an easy enough venture.
As iconic as just about every single character is within the world of Seinfeld, Kramer remains the most unique and one-of-a-kind, although I guess that can be widened to two of a kind now that Jerry Seinfeld has welcomed the idea of Andy Kaufman being a suitable replacement for Michael Richards.