LaMarche's first entrance into the voiceover industry was in 1980 in Easter Fever and Take Me Up to the Ball Game, two Canadian films from Nelvana. LaMarche did not venture into voiceover acting again until years later as a side endeavor during his full-time standup comedy career.
LaMarche began on Inspector Gadget and went on to Dennis the Menace, Popeye and Son and The Real Ghostbusters. After The Real Ghostbusters, LaMarche became a regular mainstay of the voiceover industry appearing in such shows as Talespin, Tiny Toon Adventures, GI Joe, Attack of the Killer Tomatoes: The Animated Series, Taz-Mania, Where's Waldo, The Little Mermaid, Batman: The Animated Series, and Bonkers before landing perhaps his most recognized role in 1993 as The Brain on Animaniacs (and later its spin-off show Pinky and the Brain). Following this, LaMarche worked on The Critic, Freakazoid!, and The Tick before then reprising his role of Egon in Extreme Ghostbusters. The stretch of two years after this saw LaMarche portray characters in such shows as Duckman, Hey Arnold! as Big Bob Pataki, Queer Duck, King of the Hill, The Chimp Channel, and Sonic Underground as Sleet. During this time Maurice would become the voice actor for Mortimer Mouse who he would voice in the television series Mickey Mouse Works and Disney's House of Mouse. It was at this time, 1999, that LaMarche began work on Futurama. He won the Primetime Emmy Award for Outstanding Voice-Over Performance in 2011 for portraying Orson Welles' head and Lrrr in the episode "Lrrreconcilable Ndndifferences". Since Futurama LaMarche has continued to work steadily in television, including guest roles on The Simpsons (where he once again parodied Orson Welles). His most recent regular role came as Hovis the butler on the Nickelodeon series Catscratch.
LaMarche has done various voice work for many Warner Bros. Animation and DiC Entertainment cartoons. He also delivered the protracted belches for the "Great Wakkorotti" shorts on Animaniacs, in which Wakko Warner performed various pieces of music. In 2011, LaMarche reprises his role as Yosemite Sam in Cartoon Network's new series, The Looney Tunes Show.
Pinky and the Brain
LaMarche plays the character of The Brain in Pinky and the Brain. In creating the voice for Brain, LaMarche says he looked at a picture of the character and immediately thought of Orson Welles, although the character wasn't modeled after Welles. Voicing Brain gave LaMarche the opportunity to make use of his signature impersonation of Welles. Many Pinky and the Brain episodes are nods to Welles' career. LaMarche won an Annie Award for his role as the Brain, and was nominated for an Emmy. Lamarche would later use this accent to voice Father in Codename: Kids Next Door.
His time on The Critic also afforded LaMarche the opportunity to once again parody Orson Welles, this time after a video reading of a will (the Sherman family was so wealthy, they had hired Welles to narrate it) dissolves into a commercial for Mrs. Pells Fishsticks (as well as another for Rosebud Frozen Peas, and another for Blotto Bros. wine).
The Inspector Gadget universe
LaMarche has voiced Inspector Gadget (originally voiced by Don Adams) in two Inspector Gadget films (direct-to-video and television movies) as well as two television series (the original, and Gadget and the Gadgetinis), plus two live-action appearances in The Super Mario Bros. Super Show! LaMarche also voiced Chief Quimby.
LaMarche acted, voice only, in the second episode of the hit NBC show Heroes, "Don't Look Back", as the villain Sylar. His voice is heard in a chilling recorded phone conversation on Chandra Suresh's answering machine. The role of Sylar was later played by Zachary Quinto.