"Bats In The Belfry" promises to be a kind of Gothic treat; but when the title trio appear on the scene, our hopes are deflated with another group of cutely drawn cartoon mice, straight out of its own time, the early 40s. The song of the same name—another sadly forgotten part of America's pop-song heritage--serves as the framework for the characters' antics.
The song's (and cartoon's) name derives from an old colloquialism, referring to someone mentally unbalanced.
The three bats are a tall one who talks in a dumb-Bronx accent; a considerably shorter middle one with a raspy, high-pitched voice; and a little shrimp named "Brickbat" who's totally pantomime (i.e., non-speaking) and who merely nods or shakes his head as a response. Oh, and he hiccups a lot, too.
The three characterizations are very, very well-defined—no mystery, as this was MGM, the no-expense-spared studio whose budgets were the envy of all other animation studios. There's one early cartoon attempt to "break the fourth wall," when the strapping one sees us, the audience, from a sleepy bat's perspective. In frustration, he commands that the theater be turned upside down! A moment of pathos, too, when he nearly falls to his death (false alarm, of course), and the midsized bat must console the mourning Brickbat.
(Worth noting is that the song "Bats In The Belfry" was later used as the theme music for the 1955 Bugs Bunny cartoon "Hare Brush"—or a simulation thereof, since the original tune was most likely copyrighted by another studio.)