The Three Stooges: We Want Our Mummy (1939)

When Professor Tuttle is kidnapped from the Museum of Ancient History, museum directors hire three detectives (Moe, Larry, and Curly) to track him down and retrieve a stolen mummy. While in Cairo, the detectives inadvertently stumble into the kidnappers' lair inside the tomb of King Rootin-Tootin. Despite encountering skeletons, mummies, and crocodiles, the detectives manage to outwit the thieves, rescue the professor, and find the valuable artifact. Originally released in February 1939.

Donald Duck: Donald's Lucky Day (1939)

Little Rascals: Alfalfa's Aunt (1939)

I once recorded this episode off TV in the late 80s or early 90s, but only caught the tail end of it. The storyline doesn't involve Halloween, but it does include elements that fit the holiday mood. Alfalfa's aunt Penelope is a mystery writer who comes to visit. Alfalfa finds a page from a story she is writing, which is in the form of a letter. It reads:

Dear X,

I have discovered that only my nephew stands between me and the Switzer millions! So like the others, he shall die in agony - tonight - at the stroke of nine!

Believing that his own aunt is planning to murder him, Alfalfa recruits the gang to help protect him from her.