One of the many notorious 70's "unknown" documentaries, The Mysterious Monsters covers topics such as Bigfoot and the Loch Ness Monster. Pictures, sounds, and videos of these two monsters are examined by Peter Graves, the host. Psychics, hypnotism, and the history of Bigfoot in many ancient cultures is also scrutinized.
| Actor | Role |
|---|---|
 Peter GravesHimself - Narrator | Himself - Narrator |
| PPeter HurkosHimself | Himself |
| WWilliam StenbergHimself | Himself |
| SSidney WalterHimself (as Dr. Sidney Walter) | Himself (as Dr. Sidney Walter) |
| JJerilou WhelchelHerself | Herself |
 Roger PattersonArchive Footage | Archive Footage |
| PPeter C. ByrneSelf | Self |
| GGrover KrantzSelf | Self |
| AAdrian ShineLoch Ness Investigator | Loch Ness Investigator |
| RRobert W. MorganSelf | Self |
| JJohn GreenSelf | Self |