Mysterious Mose (1930)

Although her character was still in the early developmental phase, with puppy ears and a darker complexion, the atmospheric and haunting Mysterious Mose was the fourth Talkartoons animated short to feature Betty (voiced here by Margie Hines), but she was not yet known as Betty Boop at this point (she would not be named Betty Boop until the episode Silly Scandals in 1931). She's nameless here, but she was referred to as ?Nancy Lee? in a previous episode, Barnacle Bill (1930).

Mysterious Mose is one spooky, fun episode with a bit of a gothic horror slant to it. Part of its success as an eerie cartoon comes from the ghostly sound effects at the beginning, with Betty being awoken at night by a serious haunting. The cartoon takes a stylish turn when spooked Betty slips out of bed in her nightgown to explore the dark house with a lit candle. The antics ramp up when Betty breaks into the episode's theme song, before being joined by ghostly Bimbo and other midnight spooks.

Mysterious Mose would definitely pair well with Betty Boop's Hallowe'en Party (1933) and has been noted for brief flashes of quasi-nudity a couple times when Betty cartoonishly has the shirt scared off of her, which was most risque for the time.