In preparation for their book, "The Films of Errol Flynn," authors Clifford McCarthy, Rudy Behlmer, and Tony Thomas arranged for a screening of Don't Bet on Blondes (1935) at Warners. However, the studio's nitrate print was in such bad shape that Warner decided to destroy the print because of its deteriorating, highly flammable state.
At the shoeshine stand, in the background can be seen an advertising poster for "Roya Engal" cigars. That is a real poster for a real product - Royal Bengals cigars - with three letters obviously painted over. The cigars were actually cigarillos (aka cheroots) and sold in packs of ten for fifteen cents at the time of this film - which can be seen on the poster (the equivalent of $3.36 in 2023).
Errol Flynn appears briefly playing a bit part in his fifth movie, and second in Hollywood, just before his break-through role in Captain Blood (1935) later that year. He made the movie shortly after his marriage to Lili Damita.
Odds' real first name - Oscar - isn't revealed until the very end of the film.
One of the drugs Odds finds in Markham's horse is papaverine, an opium derivative. One of its actions is as a coronary vasodilator, which would allow the horse's heart to work harder.