Alfredo "Fred" Armisen (born December 4, 1966) is an American actor, comedian and musician best known for his work as a cast member on Saturday Night Live, and portraying off-color foreigners in various comedy films such as EuroTrip, Cop Out or Anchorman: The Legend of Ron Burgundy. With Carrie Brownstein, he is the co-creator and co-star of the IFC sketch series Portlandia. He also recently voices Speedy Gonzales in The Looney Tunes Show on Cartoon Network. Description above from the Wikipedia article Fred Armisen, licensed under CC-BY-SA,full list of contributors on Wikipedia.

Fred Armisen plays as Various Characters in Moonbase 8.
Fred Armisen is the top #1 member of the cast and appears in 27 episodes.

John Christopher Reilly (born May 24, 1965), better known as John C. Reilly is an American film and theatre actor. Debuting in Casualties of War in 1989, he is one of several actors whose careers were launched by Brian De Palma. To date, he has appeared in more than fifty films, including three separate films in 2002, each of which was nominated for the Academy Award for Best Picture. He was nominated for an Academy Award for Best Supporting Actor for his role in Chicago and a Grammy Award for the song "Walk Hard", which he performed in Walk Hard: The Dewey Cox Story. Description above from the Wikipedia article John C. Reilly, licensed under CC-BY-SA, full list of contributors on Wikipedia.

John C. Reilly plays as Jerry Buss in Moonbase 8.
John C. Reilly is the top #2 member of the cast and appears in 10 episodes.

Timothy Richard Heidecker (/ˈhaɪdɛkər/; born 3 February 1976; Allentown) is an American comedian, writer, director, producer, actor and musician. He is best known as one half of the comedy duo Tim & Eric (along with Eric Wareheim) and as co-host of the parodic film review web series "On Cinema" (alongside Gregg Turkington). Tim & Eric are noted for creating the television shows "Tom Goes to the Mayor" (2004-2006), "Tim and Eric Awesome Show, Great Job!" (2007-2010), "Check It Out! with Dr. Steve Brule" (2010-2017), "Tim and Eric's Bedtime Stories" (2013-2017) and "Beef House" (2020). Tim & Gregg, in addition to the fictional "On Cinema" universe, created shows around it such as "Decker" (2014-2017), "The Trial" (2017), "Mister America" (2019) and "Annual 'On Cinema' Oscar Specials" (which are broadcast live). Heidecker has also acted in several films, including "Bridesmaids" (2011), "Tim and Eric's Billion Dollar Movie" (2012), "The Comedy" (2012), "Entertainment" (2015), "Brigsby Bear" (2017), a bit part in "Ant-Man and the Wasp" (2018), and "Us" (2019).

Tim Heidecker plays as Rook in Moonbase 8.
Tim Heidecker is the top #3 member of the cast and appears in 6 episodes.