There are always little characters popping up to enliven the Fleischer Talkartoons. In Mask-A-Raid (1931), Betty Boop hands swords to Bimbo and the King so they can duel over here. Soon, a phalanx of armoured soldiers marches forward to join in. One of them apparently gets killed.
Cut to a scene where a trap door on the armour opens up and a mask pops up. Yes, there are masks all over the cartoon, but that but that isn’t the gag. A mouse pops out, makes a spitting scat of the words “Give a piece of pie” in time to the music. His job done, he disappears for the rest of the cartoon. The reference must be vaudevillian, but I couldn’t tell you from where.
The cartoon ends with a great scat by Bimbo with winged Betty Boops in the air. Great stuff. Unfortunately, there are no animation credits.