The basic plot is actually as amusing as it is nonsensical. Jim Moore (Allan Jones) is in the insurance game and his company will insure everything. When his friend Steve Harper (Robert Cummings) starts to get himself flustered about things not going according to plan as he attempts to wed the woman he loves (Cynthia Merrick, played by Nancy Kelly), Jim manages to somehow sell him on the idea of an insurance policy for love. IF Steve and Cynthia don't get married when planned then Steve stands to gain a million dollars. Of course, Jim can't afford to pay out that kind of money so he goes to great lengths to keep things on track despite the efforts of a disapproving aunt (Mary Boland), another woman (Peggy Moran) in love with Steve and the unfortunate fact that Jim himself finds Cynthia pretty darned attractive. Things get farcical while Abbott & Costello stay on hand to also ensure that the wedding goes as planned. So you can probably guess how ill-fated the whole thing seems.
Based on the novel "Love Insurance" by Earl Derr Biggers, One Night In The Tropics is actually a decent enough old movie that I wouldn't mind seeing updated and remade for 21st century audiences. The central idea is a high-concept one and has potential but this film has been made as both a general comedy, with occasional musical moments, and a showcase for Abbott & Costello and it's the scenes that allow the comedy duo to show their strengths that ended up providing the most entertainment.
The screenplay, worked on by a number of folk, is okay for the material, the acting is perfectly acceptable for a 1940 film and the direction by A. Edward Sutherland does enough to put this on a par with many other lightweight movies of the time but let's make no bones about it - this movie would be forgotten and consigned to the wastebin of cinema if it didn't have some superb, slick comedy routines in there, including a version of the legendary (and rightly so) "Who's on first?" routine.
So, overall, it's no bona fide classic but because of the few scenes interspersed throughout including some absolutely wonderful A & C skits it remains well worth a watch to comedy fans.