- “My name is Michael J. Caboose, and I hate babies!”
- — Caboose
Michael J. Caboose is voiced by Joel Heyman. Caboose first appears in episode 3 of season 1 as a new recruit for the Blood Gulch Blue Team, a group of soldiers engaged in a futuristic civil war against the Red Team.
Caboose is portrayed as one of the most eccentric characters in the series. Consistently shown to be mentally abnormal, his behavior varies from merely somewhat dim-witted in Season 1 to almost completely divorced from reality in Season 3 and onwards. This is most likely due to the strong possibility of Omega (aka 'O'Malley') possessing him in Season 1 and probably turning his mental faculties into something that probably resembles a radioactive train wreck. Assuming, of course, that he had such mental faculties in the first place. Or that the whole thing wasn't just a ruse to disguise his true abilities. His unusual behavior frequently earns him the scorn and disrespect of the series' other characters. It is a running gag that he injures or kills anyone that he attempts to help. In several instances, characters get him to shoot targets by telling him that "they are friends and we are trying to help them". In the original series, he killed Alpha-Church with the Blue Team's tank, Sheila. In Reconstruction, while the cast is being assembled, Washington finds him in a military stockade, apparently for accidentally killing several squad-mates. Later in Reconstruction, in an attempt to stop Freelancer Agent South Dakota, Church tells Caboose to "Help her", in which Caboose immediately shoots her. Despite his shortcomings, Caboose is arguably the most genuinely loyal character and frequently displays above-average physical strength.
Oddly enough, whenever Church possesses Caboose (allowing viewers to see inside the workings of Caboose's mind), Caboose's mental representation of himself seems completely sane and reasonable, like a calmer version of how he acted in his first few episodes before he was taken over by O'Malley. A few episodes take place partly in Caboose's mind, and it is shown that he pays little attention to what some of Red Team look and act like. For example, Sarge spoke like a pirate, Grif originally was yellow (Before Sister came), Simmons was called Simnon, Donut was a girl, and Sister was "Church's twin brother that crashed from the moon and now lives with Caboose and the people from the tail section of the space ship now live on the other side of the island."
According the backstory released by Rooster Teeth, Caboose is the youngest in a large family. He apparently joined the Blue Army by mistake; he thought he was signing up for a study abroad program in France.
In an early episode of the Drunk Tank Podcast, a series of candid conversations between the creators of Red vs. Blue, Joel Heyman, Caboose's voice actor, revealed that his motivation for the character was that Caboose is "the only character who is aware that he's in a video game."
In the first few series Caboose falls in love with Sheila the tank, but loses her when Lopez comes into the picture. Caboose is the one who brings Epsilon-Church to Vallhala and the desert area with Tucker in the hopes of getting a new best friend.
- "Caboose" is the last wagon of a train, highlighting how the character's train of thought is always late. His full name is a reference to actor Michael J. Fox, and may also be a reference to Burnie Burns' given name, "Michael J. Burns".
- Beginning with Red vs. Blue: Reconstruction, Caboose is easily identifiable for still having the Mjolnir Mark V helmet from the original Halo, while everyone else has moved onto Mark VI. Due to the helmet not being available right away on Halo 4, Season 11 had him wearing the Mark VI helmet until the original one was put up as DLC, with Caboose getting a Mark V helmet in episode 15.
- This helps him in the latter half of Red vs. Blue: Revelation where Caboose is the only person not to go into armor lock in a move to stop Tex, partly because the Mark V helmet doesn't have the protocol inducing said armor lock installed into it.
- According to an alternate ending of Episode 100, as Caboose was killed in a firefight it said he pitched his life story to a software company based in Redmond, Washington, who created a best-selling video game based on it. That's a reference to Bungie and the Halo series.