Trivia

Was one of only three voice-over actors from The Transformers (1984) animated series to voice a character in the live-action film versions Transformers: Revenge of the Fallen (2009) and Transformers: Dark of the Moon (2011). The others being Charlie Adler and Frank Welker. Cullen once again provided the voice of the heroic Autobot leader Optimus Prime for the films.

Stated that of all the roles that he has done, his signature role, Optimus Prime, is his favorite. He described playing Prime in the 2007 film as "slipping into a very old, very comfortable pair of shoes". He explained his preference for the character by saying "making people happy makes me happy".

Though he provided vocals for the inhuman alien Predator in the Predator films and the voice of Eeyore in Winnie the Pooh, he is best known for voicing the heroic Autobot leader Optimus Prime on The Transformers (1984) animated series. Though this was originally intended for his character to remain dead after being killed in The Transformers: The Movie (1986), the death caused such a public backlash that the surprised producers brought the character back in two separate episodes of the third season (ultimately saving the world in the second appearance).

Has stated that the voice of legendary American film actor John Wayne had some influence on his choice for the voice of Optimus Prime. However, he clarified in an interview for the 2007 Transformers video game that the inspiration for Prime's voice was actually based on an impression of his older brother's voice -- the authoritative tone he used while serving as an officer with the Marine Corps during the Vietnam War.

Provided the roar of the title character in King Kong (1976), injuring his throat in the process. The experience turned him off of voicing inhuman sounds, though he later made an exception for Predator (1987).

His older brother, Larry Cullen, was a retired Captain in the United States Marine Corps, and helped inspire the voice of Optimus Prime.

He was the first actor to voice Nintendo's video game mascot Mario - of Super Mario Brothers - for the Saturday Supercade series.

Frequently does voice-overs for commercials, cartoons, movie previews, etc.

He is of mostly Irish descent.

Attended and graduated from Regiopolios-Notre Dame Catholic Secondary School in Kingston, Ontario.

Occasionally provides the narration for movie trailers. Most notably for Batman & Robin (1997) and Spawn (1997).

Has been the voice of two characters involved in chicken runs (when two cars drive towards each other). The first was the evil K.A.R.R. in the television series episode Trust Doesn't Rust (1982). The second was the heroic Autobot leader Optimus Prime on the animated series The Transformers (1984).

Has four children: Clay Cullen, Angus Cullen, Claire Cullen and Pilar E. Cullen.

Attended and graduated from the National Theater School of Canada in Montreal, Quebec (1963).

Father-in-law of Molly Culver.

Received the Emmy award for Lifetime achievement at the 2nd Annual Children's and Family Emmy Awards on December 17, 2023. The presenter was fellow voice actor Frank Welker.