Genius Bonus: In "The Itch", the eponymous song was sung by rats, the "dance" was actually rodential fans scratching their fleas, and the song was to the tune of "Ring Around the Rosary". And it was set in the Middle Ages. Everything about it was a reference to The Black Death.
Nightmare Fuel: The gooey alien in invasion of the body slammers. what really sells it is its freaky smile when impersonating Tom or Jerry.
Tom as an alien octopus-like creature in "Cat Nebula" can be a bit scary.
In the episode "Spook House Mouse" was really creepy, Tom and Jerry got so traumatized they both turned white.