Conversation so far:
What happened in 1940?
His first post-Ginger dance partner was the redoubtable Eleanor Powell--considered the finest female tap-dancer of her generation--in Broadway Melody.
What Broadway shows was he in?
Broadway Melody of 1940, in which they performed a celebrated extended dance routine to Cole Porter's "Begin the Beguine.

Question: Who else did he perform with?
Self-contained rewrite: Who else did Fred Astaire perform with, besides Eleanor Powell?