Starting with this film, Humphrey Bogart would always receive top billing for the rest of his career.
The lions were from Gay's Lion Farm in El Monte, California. In operation from 1925 to 1942 when it closed due to war-time meat rationing, it was a popular tourist attraction and lion breeding center.
This was the first time Bogart was top billed in an "A" picture. (He had been top billed previously in a couple of B pictures.) Ironically, this movie is a semi-remake of Kid Galahad (1937), with Bogart playing a character who is a combination of his own character and Edward G. Robinson's character in the earlier movie.