In 19th century India, three British soldiers and their native bhisti (water bearer) must stop a secret mass revival of the murderous Thuggee cult before it can rampage across the land.
Originally, Grant and Fairbanks were assigned each other's role; Grant the one leaving the army to marry Joan Fontaine's character, and since the character was identical to the legendary screen persona of Fairbanks' father, Fairbanks the happy-go-lucky treasure hunter.
According to Robert Osborne of Turner Classic Movies, when Grant wished to switch parts, director George Stevens suggested they toss a coin; Grant won and Fairbanks, Jr. lost his most important role.
Fairbanks reported in a featurette interview for the DVD release that in his travels, he had met several Hindi Indians who were convinced the external scenes were filmed on location in Northwest India at the actual Khyber Pass but in actual fact California's Sierra Nevada range, Alabama Hills and surrounding areas doubled as the Khyber Pass for the film.
The film includes an end sequence in which a fictionalised Rudyard Kipling (played by Reginald Sheffield), witnesses the events and is inspired to write his poem. Following objections from Kipling's family, the character was excised from some prints of the movie, but has since been restored.
Did you know that Gunga Din was budgeted at $1.915 million, making this the most expensive film RKO had produced to that date. It was nearly a half million over budget.