James Cagney spoke fluent Yiddish, and in this film got the opportunity to demonstrate it.
Cagney was in the dance contest with Loretta Young as his partner, and curiously, ex-hoofer and future star George Raft was his opponent vying for the first-place cup.
The movie-within-a-movie, 'Her Hour of Love', with Donald Cook and Evalyn Knapp, was not an actual film clip, but a new sequence especially filmed for 'Taxi'.
This movie is the source of James Cagney's most famous misquoted line, "You dirty rat!" In the film, Cagney actually says, "Come out and take it, you dirty, yellow-bellied rat, or I'll give it to you through the door!"