Having produced a great Christmas special 2 years before, Pinky and the Brain takes a shot at Halloween. It's hard to find a holiday as fun as Halloween, and surely Pinky and the Brain's writing staff could put it to good use. They pick surprisingly dark subject matter- Pinky sells his soul to Satan (here called Mr. Itch) and is tortured in Hell (here called Hades) so Brain can rule the world.
Probably the best part of this episode is that it puts Brain in real conflict, torn between his friendship with Pinky and his burning desire to rule the world. The episode begins with tension between the two mice after their Jack-o'-lantern plot fails (Brain blames Pinky, even though it was really Brain's fault). But then Brain realizes he can't let Pinky go.
This episode is rare example of Pinky and the Brain taking on the supernatural, but it's unlikely to scare children, even when Mr. Itch transforms into a Fantasia-style devil. Part of what helps is that Pinky actually enjoys being tortured in hell, so we don't have to feel too bad for him. Topped off with some funny lawyer jokes, A Pinky and the Brain Halloween is a memorable, fun episode.