Filming was scheduled to start on 1/30/39, but the death of The Ritz Brothers' father caused a delay of nearly a month. 20th Century-Fox brought a $150,000 breach of contract lawsuit against the brothers after they didn't show. This ended their relationship with the studio.
It's less obvious today than it was in 1939, but giving the obviously Jewish The Ritz Brothers Irish names is a typical-of-the-era ethnic joke.
The Ritz Brothers were essentially Fox's answer to The Marx Brothers, although they never achieved the same degree of critical acclaim or popular acceptance that the Marxes enjoyed.
The gorilla was no doubt named Poe as a nod to "Murders in the Rue Morgue", in which a gorilla is prominently featured.