Yeah, I think we talked about this on the old site, but Jason Alexander gave an interview just a few years after the show finished. And he goes into these stories about leaving the set to go home and he'd quietly watch/listen to Michael who has either on the set or behind it, just drilling down all these little movements and mouth clicks and mannerisms. And Jason was, and had worked with, very committed thespians. But he said that Michael treated it like a stage in that he knew they could go back during post and add emphasis to his clicks or head donks or falls, etc. But that Michael wanted to make it as loud and realistic as possible so he did most of that shit himself and had them mic it accordingly. And Jason says the truly amazing part was when Michael was doing all that goofy shit, some of which hurt him physically, he could just roll right into the dialogue be it dry or silly, and not skip a beat. And Julie and/or Jerry would crack up, but Michael broke the least of any of the 4.
I wish I could remember who Jason gave the interview to, this would have been right about 20 years ago. It wasn't terribly insightful or entertaining, nothing you couldn't glean from the DVD commentary which started coming out about that time. But to hear Jason tell it like "I've worked with committed actors on stage and screen, but how Michael could switch from painful physical comedy to dry sarcasm on a dime was something I had never seen before and didn't even really knew existed." It was like Season 2 or so the way he tells it, but he mentioned other times down the road. Much as we all love to quote the brilliant writing, and as funny as the four of them are, there really was 'lightning in a bottle' chemistry' between them that can never be replicated.