The Kelp Monster was the disquise of Mr. McFinn.
The Kelp Monster is a big glowing green seaweed creature with eye holes and mouth hole, has legs, and has arms.
The Kelp Monster a very cruel monster when helping the Ghost of Captain Pescado and the Octopus Monster trapping Velma Dinkley, Fred Jones, and Daphne Blake. The Octopus Monster seems to be hungry when he took Shaggy Rogers and Scooby-Doo's breakfast at the galley.
The Scooby-Doo Show
The Kelp Monster attacked the gang with his pals Captain Pescado and the Octopus Monster. The Kelp Monster got on board with the Captain Pescado and the Octopus Monster. He was sleeping in the control center, until the Octopus Monster chased Shaggy Rogers and Scooby-Doo and the Kelp Monster woke up and chased Velma Dinkley. The Kelp Monster and his pals found Scooby, Shaggy, and Velma in a sunken ship. The three ghosts were captured. Pescado was First Mate Carp, Kelp Monster was McFinn, and the Octopus Monster was Mr. McGil. The three criminals were taken to jail. (Scooby-Doo, Where's the Crew?)
- Its name is spoken once, by Velma.
- In Scooby-Doo! And The Goblin King, the Kelp Monster was among the monsters seen in the monster bar.