Yeah, Art Vandelay.

Who is George Costanza?

George Costanza (Jason Alexander) is Jerry’s oldest friend and the show’s patron saint of bad decisions — “Lord of the Idiots,” serial job-loser, occasional architect named Art Vandelay, and, when the moment demands it, a marine biologist. Based loosely on co-creator Larry David, which explains a lot. Appears in every episode but one, presumably because he had nowhere else to be.