This page explains in detail the interactions between the Ben 10 series and the The Grim Adventures of Billy & Mandy series.
Ben 10 episode Ben 10,000[]
The unused Fred Fredburger alien incidental, designed by Thomas Perkins.
November 25, 2006
The Grim Adventures of Billy & Mandy
Ben 10
Originally, in the Ben 10 episode: "Ben 10,000", there was supposed to be an alien incidental based off of Fred Fredburger from The Grim Adventures of Billy & Mandy, but was cut.
Ben 10 episode Ken 10[]
October 6, 2007
The Grim Adventures of Billy & Mandy
Ben 10
In "Ken 10", one of the guest at Kenny's 10th birthday party is an orange alien named Billy, who is designed to be a homage of Billy from The Grim Adventures of Billy & Mandy, complete with a bulbous pink nose, a red hat and a blue and white striped shirt. He is even voiced by Billy's voice actor, Richard Horvitz.
The name of Billy's species, the Maxatomar, might also be derived from the name of Maxwell Atoms, the creator of Billy & Mandy.
Ben 10: Omniverse episode Special Delivery[]
February 2, 2015
The Grim Adventures of Billy & Mandy
Ben 10
In the Ben 10: Omniverse episode: "Special Delivery", Billy makes an appearance in the background at Psyphon's auction.
Ben 10: Omniverse episode Bengeance is Mine[]
October 6, 2007
The Grim Adventures of Billy & Mandy
Ben 10
In "Bengeance is Mine", Billy watches one of Vilgax's holograms as they appear throughout Undertown.
Ben 10: Omniverse episode No Honor Among Bros[]
October 6, 2007
The Grim Adventures of Billy & Mandy
Ben 10
In "No Honor Among Bros", Billy was part of the audience of the Golden Fist Tournament.
Ben 10: Omniverse episode Clyde Five[]
October 6, 2007
The Grim Adventures of Billy & Mandy
Ben 10
In "No Honor Among Bros", Billy can be seen in the background of the Black Hole.
License[]
Both series are owned by Cartoon Network, however, Man of Action only chose to include a minor reference to the series in both Ben 10 and Ben 10: Omniverse.