Basil Rathbone and Nigel Bruce are playing themselves, seen on the Universal studio lot. They call each other "Holmes" and "Watson" as a joke because they were currently playing these characters in Universal movies.
As a gag veteran performers Andy Devine, Leo Carillo, Basil Rathbone, Nigel Bruce, Johnny Mack Brown and Allan Jones, all of whom make cameos, are given a special "Introducing" title card.