Robin Williams is pretty much a "one note" Actor. If you have seen him in one movie,you have pretty much seen him in all of his movies.
You must be thinking of someone else cause I don't see any simularities in these characters Williams has played
Popeye in Popeye ,
Rainbow Randolph in Death to Smochie,
Sy Parrish in One Hour Photo,
Sean Maguire Good in Will Hunting,
Armand Goldman in The Birdcage ,
Mrs. Doubtfire in Mrs. Doubtfire ,
Adrian Cronauer in Good Morning, Vietnam