RKO wasn't planning a series while this film was being made, but the "Mexican Spitfire" series developed after it was such a big hit. In total, the studio released eight films in the series, starting with this picture, from 1939 to 1943.
The airplane depicted as the one Denny flies in to Mexico is an American Airlines Douglas DST-144/DC-3 named "Flagship Illinois", built in 1936, registration NC16002. This particular plane is interesting because on a charter flight between San Juan, Puerto Rico and Miami, Florida on 28 December 1948 it and all 32 aboard would disappear, and thus enter the lore of the Bermuda Triangle. This same aircraft can also be seen in Flight Angels (1940).
Carmelita tells Matt she wants to "kick the gong around." The casual use of this expression suggests that the writers thought it meant "going out on the town" instead of its actual meaning: smoking opium.
This film led to a series in which Velez played the same character, referred to in the titles of seven sequels as The Mexican Spitfire. When the franchise ended in 1944 and Velez found herself unwed and pregnant with no prospect of marriage, rather than abort the child, she took her own life in an elaborately staged suicide that guaranteed her international news coverage.
This is the sole picture in which Leon Errol plays only Uncle Matt. His other character, Lord Basil Epping, was created for the second film in the series, "Mexican Spitfire," and appeared in all subsequent entries.