Big Bull Demon is a minor antagonist in the TV series OK K.O. Let's Be Heroes.
He was voiced by Michael-Leon Wooley.
He first appeared in "You Have to Care" fighting Elodie from P.O.I.N.T. Academy.
He then appeared in "Villains Night Out" as one of the many villain guests invited to Billiam Milliam's party. He can be seen talking to Vormulax. He then tries to sing karaoke with her but is interrupted by Lord Boxman and his shenanigans. When Lord Boxman tries to destroy P.O.I.N.T. Headquarters the missiles are redirected towards the party boat. This causes Big Bull Demon and the rest of the Villains at the party to evacuate.
He appears in the short "Action News" where he fights off against Ted the Viking at Lakewood Plaza Turbo. He appears as one of K.O.'s pow cards in "Mystery Science Fair 201X." He also has a short appearance in "Lets Not Be Skeletons" where Gill Ferris shows a demonstration of the his skeleton remote to the heroes of Lakewood Plaza Turbo.
He appears in "Seasons Change" where he attacks the Plaza and easily defeats Rad and Enid due to their new changes. He then grabs K.O. and starts crushing him in his hand. However, Rad and Enid go back to their old selves and quickly defeat him.
- His original name was supposed to be Cyborg Demon Soldier Overlord but got changed to Big Bull Demon.
- Big Bull Demon is the second non-Boxmore robot to attack Lakewood Plaza Turbo, the First being Steamborg.
- In "You're a Good Friend, KO" he is revealed to have a nephew named Small Calf Demon.