Allen the Alien is a supporting character and superhero in the comic book series Invincible and it's 2021 Amazon adaptation.
In the animated series, he is voiced by Seth Rogen, who also played himself in This is The End, Paul in the 2011 film of the same name, Mac Radner in Neighbors, Mantis in Kung-Fu Panda, B.O.B in Monsters vs. Aliens, Morton the Mouse in Horton Hears a Who!, Hogsqueal in The Spiderwick Chronicles, Frank in Sausage Party and Pumbaa in the 2019 remake of The Lion King.
Genetically engineered on his homeworld to battle the alien conquerors the Viltrimites, Allen was born with fantastic strength. Still not strong enough to challenge the Viltrimites, he became the Champion Evaluation Officer for the intergalactic organization The Coalition of Planets with the job to test the strengths of the champion of each planet.
Allen was born in a breeding camp for his people, the alien race known as Unopans. As his species was nearly exterminated by the conquering spacefaring race known as the Viltrimites, Allen was bred to be the strongest possible member of his race capable of standing toe-to-toe with the extremely powerful aliens.