Mad Monster Party(1967)
When Baron Von Frankenstein discovers the formula for a powerful anti-matter potion, he gathers all of the monsters -- and his nebbish nephew Felix -- for a party to announce his retirement. But the monsters aren't happy that he's named Felix as his successor, so they scheme to rub out the mortal.
This 'animagic' feature from Rankin/Bass (Rudolph the Red Nosed Reindeer) bombed theatrically but got a cult following from airings on TV, as well as on video & DVD. Director Tim Burton cites this as the inspiration for THE NIGHTMARE BEFORE CHRISTMAS. Followed by the animated prequel MAD, MAD, MAD MONSTERS.
This trailer was originally uploaded to YouTube by IMACACI.