You are probably thinking of “Way Out West”, which has that delightful “Commence the Dancing” Dance in it.
Those gags Stan called “White Magic”, and he used it more and more as time went on.
I’d say look for the Dance on Youtube, but it has become a meme, so the original is hard to find.
Here, however, is a Way Out West Page for you.
http://lhwayoutwest.angelfire.com/trivia.html
I know the dance well -- we must have Way Out West, because we are prone to watch the movie and replay that scene a time or two because it's so funny. Ollie must have been (physical-wise) a bit like Chris Farley (another hilarioius comedian, and I still mourn his passing) in that he was pretty physically fit and athletic, believe it or not, under all that generous marbling. I think that the hippos in Fantasia must have been inspired by Ollie!
And you can see that the musicians are highly amused by the duo! It's fun to watch.