Mad Monster Party (1967) is an American animated comedy film produced by Rankin/Bass Productions (yes- the same people who animated our Christmas childhoods: Rudolph, The Year Without a Santa Claus, etc) and is one of the best and deserves its wonderful cult status.
Here is a little bit of the story line: Baron Boris von Frankenstein (voiced by none other than Boris Karloff) is set to retire, especially since he has just finished the most important formula to date. It is time for him to pick and announce his heir and the new head of Worldwide Organization of Monsters. He sends out his faithful messenger bats to deliver the invitations. There's Fang (Frankenstein's Monster), Fang's mate (voiced by Phyllis Diller), Count Dracula, the Mummy, Quasimodo (aka "The Hunchback of Notre Dame"), the Werewolf, The Invisible Man, Dr. Jekyll and Mr. Hyde, the Creature from the Black Lagoon, and Felix Flanken (the Baron's nephew). "It" of course was not invited, because of previous party fouls. Of course there is also the Baron's staff: his assistant Francesca (who looks just like Christina Hendricks, especially as her character Joan from Madmen), Yetch (the zombie butler), Chef Mafia Machiavelli, and other zombie bellhops and servants, plus musical skeletons. Competition gives way once the news is revealed, not to mention "It" arriving anyway to stir things up.
And that is all I will tell you, because if you haven't seen this film, then you should definitely make it a must this Halloween season. If you need any more reasons, I decided some fan art could definitely do the trick. Hope you enjoy the selection and maybe get inspired to make you own.