Whoever was directing “The Brementown Musicians” for Ub Iwerks tried an effect that other studios used later but didn’t have the technical expertise in 1935 to pull it off.
The background changes behind some characters while they’re still walking. The only problem is the method they chose was to double-expose the animation during the background transition, and the animation doesn’t match up. You see ghost imagines.
No animator credits appear on any the ComiColor cartoons, Iwerks’ version of the We’ve-Got-to-Make-it-Look-Like-Disney shorts that every studio inflicted on people, featuring children or animals and a bad guy everyone beats up at the end. Iwerks’ contract ran out in 1936.