Ernie is the main antagonist in SMG4: If Mario was in... Fall Guys.
He is a red Fall Guy with a cactus costume.
When his brother Bert was crowned king of the Fall Guys, Ernie became jealous of him, so he broke his legs, stole his crown, and became king of the Fall Guy Kingdom.
Afterwards, he forced the Fall Guys to participate in obstacle courses, murdering failed contestants (such as the Scout), and turning them into costumes. Others (such as Chunky) died attempting to perform his challenges.
His reign of terror came to an end when Mario breaks the costume-making machine, races him in a Fall Guys-style obstacle course, reaches the crown in his office first, and gives it back to his brother.
He is last seen outside Peach's castle, during Mario and the Fall Guy's party, tied up having things thrown at him by the Fall Guys, while screaming "Curse you, Perry the Platypus!"
- His brother's and his names are references to Bert and Ernie from Sesame Street.
- He can be considered one of the evilest villains on the show, as he murders failing contestants in Fall Guys to turn them into merchandise.
- His quote is Dr. Heinz Doofenshmirtz's quote from Phineas and Ferb.