The character is notable for having a close resemblance to George, and possesses the same neurotic, worried nature that made George famous. This was made abundantly clear when Michael had a panic attack right before the filming of the pilot began and he confided to Jerry that he had forgotten all of his lines and was going to put in a horrible performance.
George Costanza was not impressed by Michael's portrayal of him at all, and was even heard remarking to one of the crew members, 'This guy stinks.' He said this after Michael read one of his lines during rehearsal.
“The Pilot” (Parts 1 & 2)