Name:Michael J. Caboose
Homeworld: Earth Moon
Affiliation: Blood Gulch Blue Practice Team
Caboose made his first appearance in Episode 3 along with Sheila. He soon annoyed his new teammates, and consequently was tasked with guarding the flag inside the team's base and waiting for a nonexistent general. Meanwhile, at the Red base, Simmons and Grif sent their team's rookie, Donut, on a fool's errand for elbow grease and "headlight fluid." In a mutual misunderstanding, Donut mistook the Blue base for the store and Caboose for a shopkeeper, while Caboose mistook Donut for the "General" and allowed him to take the flag. In the ensuing conflict, Caboose accidentally killed Church while using Sheila, and narrowly escapes a bombing run that disabled the tank. In the final episode of Season 1, Caboose became possessed by O'Malley, a rogue AI who transmitted himself to Caboose via radio before his original host, Tex , died. Once, when he was radioing Church, he said, "Church! Come in Church! This is your close personal friend, Private O'Malley."
Season 2 continues Caboose's character development. Parts of episodes 31-33 take place inside Caboose's mind, which Church and Tex explore as ghosts in an attempt to kill O'Malley. There, they encounter Caboose's incorrect mental images of other characters. In his mind, Caboose believes that he is intelligent, Church is his foul-mouthed best friend, Tucker is stupid, Grif is yellow-armored, Donut is female, and that Sarge sounds like a pirate. In the fighting that ensued between Tex, Church, and O'Malley, Caboose's mental picture of Church was accidentally shot, thereby erasing him from Caboose's memory completely. Once O'Malley leaves Caboose, the latter's mind declines further, even going as far as loading his guns with crayons and misspelling his own name. Sarge states in episode 39 that it "sounds like he took some of the furniture when he left. And the carpet. And the drapes. And I wouldn't expect to get that deposit back, if you know what I mean."
Caboose is incredibly strong, able to carry Andy (the bomb), which neither Sarge nor Grif could even move and Tex admitted to being unable to carry; this is significant in that Tex was previously shown flipping Sheila over with her bare hands, which makes Caboose stronger than that. Tucker and Church believe this is "God's way of compensating" for his mental disabilities.
Though Caboose is generally portrayed as relatively passive, he will have brief episodes of violence in which he speaks in an exceptionally low voice. In Episode 40, Caboose "tapped" into his violent side in order to save both himself and Sarge from the Flag-Zealots by thinking of kittens covered in spikes and other things he considered mean. As a result, he started saying violent threats like "I will eat your unhappiness!" before promptly killing all of the Flag-Zealots.
In Episode 1 of the new Relocated series, he seems to be hard at work at his new base on something that wasn't revealed at the time. In Episode 4 of the Relocated series, Caboose makes a very brief appearance. Caboose's behavior in Episode 4 implied that he is losing his mind due to Church's absence. Caboose was collecting any possessions he could find that held any sort of sentimental value to him, which included Church's signature Sniper Rifle, a device that's believed to be storing Sheila, Tex's corpse and armor, and the Epsilon A.I. In addition, Caboose spoke only once in the episode, using a disturbing and shaken tone as he said "Finally, we're all here. Now we can be together... forever." In Recreation Episode 2, it is revealed that this was part of his plot to create a "super new best friend". Over this time, it has been revealed that he has been telling Epsilon about the events that had occurred during the series run, which was alterred heavily due to Caboose's incorrect memorization of it; one notable modification was removing Tucker altogether, which led Epsilon to confuse him for Captain Butch Flowers. The other notable edit would be that Sarge is the Captain of the Red's pirate ship, though this wasn't obvious at first, due to Epsilon's rather accurate initial description of Sarge. Another thing that should be noted is that, at first, due most likely to Caboose mixing something up in the description, Epsilon initially believed that Sarge was Simmons.
In terms of combat capability, Caboose seems to be somewhat capable, as he was able to defeat the Flag-Zealots rather easily after unleashing his "inner anger." Also, due to a tutorial that was run by Sheila in an early episode, Caboose also knows how to drive and use a tank. Despite that, these feats seem down-played by the fact that he generally only uses these traits to accidentally kill members of his own team. For instance, during a test run with Sheila, Caboose killed Church with the tank's cannon, though it should be noted that this particular event was later revealed to have been caused by Church's going back in time and, in this instance, turning off Sheila's friendly fire function. Church later uses Caboose's team killing skills rather efficiently, as he told Caboose to protect South during a run to capture both her and the Meta. This caused Caboose to accidentally shoot and critically wound South during her escape.
During season 9, during Epsilon's corrupted memories on the series, Caboose doesn't seem to maintain his relationship with Sheila due to Sheila not being a program integrated into the tank, though for what reason or even if this is true will be revealed in the future.
Caboose has become one of the more popular characters in the series, and in 2005, Caboose was selected as the Best Male Performance in the 3rd Annual Rockets on Prisoner Awards,<ref name="RoP3">The 3rd Annual "Rockets on Prisoner Awards.</ref> which are intended to recognize exemplary work in Halo machinima. In his acceptance speech, Joel Heyman acted in-character.