Mad Monster Party?

Baron Boris von Frankenstein, tired of creating monsters, decides to retire and calls the world's most famous creatures to a gathering so he can name a successor. Dracula, the Werewolf, the Creature from the Black Lagoon, Dr Jekyll and Mr Hyde, and others attend, but the Baron's plan to hand his position and secrets to his bumbling nephew Felix Flankin does not sit well with them. The Baron also guards a discovery of terrible destructive power, which must not fall into the wrong hands.

This Rankin/Bass stop-motion animated comedy was directed by Jules Bass, the first of twelve films he directed, followed by The Little Drummer Boy, Frosty the Snowman and others. Boris Karloff voices Baron Frankenstein, with Allen Swift providing several monster voices, Gale Garnett as Francesca, Phyllis Diller as the Monster's Mate, and Ethel Ennis singing the title song. The screenplay is by Forrest J. Ackerman, Len Korobkin and Harvey Kurtzman.

Released in 1967, the film runs 95 minutes. On IMDb it holds 6.6/10 from around 4,000 votes, while on TMDB it has 6.5/10 from 78 votes; a critics' rating of 6.2/10 from nine reviews places it close to the audience scores, suggesting broad agreement rather than a sharp divide.