Something that I've often noticed when watching the show is that there are moments when a character smirks slightly in response to something that another character says. Often times it happens when one of the actors might be improvising. There are some well documented instances where the actors nearly broke character or had a reaction that was entirely unscripted that made the show, but I'd love to see a compilation of some kind that shows more of these subtle moments.
A few that come to mind off the top of my head:
- When Andy quotes I'll Be There For You by Bon Jovi as a promise to David Wallace that he won't go on any more surprise trips, David smirks a bit as if he's holding back laughter in Moving On
- When Michael says "TDB" instead of "TBD," Ryan barely stops a smile from coming on in Night Out
- Kelly is actually just completely breaking in the background while Kevin sits on Michael's lap during Secret Santa
There are undoubtedly more. It'd be amazing if anyone out there who happens to read this could comment with any instances they know of.