Stumbled across this while doing research for a book. Cab Calloway fairly well known to modern audiences because of the Blues Brothers, but the Nicholas Brothers were active in the 1930s-1950s and thought of as the greatest tap dancers of their generation, if not of all time. Wiki says they were in a lot of movies, but their scenes would be filmed apart from the rest of the cast and having nothing to do from the plot so they could be easily cut from the movie when it played in certain parts of the country.

These guys are phenomenal. This is from a 1943 movie called Stormy Weather. If you have no patience, fast-forward to the 1:30 mark when Calloway introduces them.