The Mysterious Monsters (also known as Bigfoot: The Mysterious Monster) is a 1976 documentary film written and directed by Robert Guenette about the cryptids Bigfoot, the Loch Ness Monster, and the Yeti. It contained content from Guenette’s made-for-TV movie Monsters! Mysteries or Myths? that aired on CBS on November 25, 1974. That version had been produced by David L. Wolper in cooperation with the Smithsonian Institution and was narrated by Rod Serling.