Mitchell "Mitch" Bueller was a member of the United States Colonial Marine Corps in 2192. He was part of a Marine detachment sent to acquire a Xenomorph specimen for the Government. Bueller later grew close to the "civilian advisor" of the mission to the protests of Sergent Wilks. He would be one of two Marines to survive the botched mission and return to Earth, which unknown to the survivors, was overran by the xenomorph menace.
Bueller; along with Billie and Sergeant Wilks would escape Earth and wound up encountering the sociopathic General Spears as one of his "guests" in his facility. Bueller would later take part in the mutiny against Spears by manning the atmospheric controls for the base. Bueller was unintentionally abandoned during the skirmish between Spears's troops, the rebelling Marines and the xenomorphs. Bueller's subsequent fate is unknown after the creatures overran the base.
Mitchell Bueller was created for a future retrieval mission for the Terran Government in the later years of the 22nd century. During his time being created Mitch and the other Synthetic Marines heard a rumor of and advanced model synth that believed itself to be a live human being and could pass for human unless lab tests were done. Bueller would later be trained as a Colonial Marine, believing it to be the closest thing to family.
Training and Meeting Billie
In early 2192, Bueller and the other synthetic Marines were running training exercises with their new Sergent, David Wilks. Bueller ran one combat simulation with his good friend and fellow squadmate Easley against Sergent Wilks. During this exercise, Easley discussed with Bueller on disabling the automated turrent that had them pinned down. Bueller then attempted to draw the turrent's fire while Easley disabled the turrent. Bueller then heard a grenade go off and the turrent stop firing, thinking Easley stopped the turrent, Bueller then stood up to cheer but was shot with a paint round on his chest. Wilks, then chastised the two for how they ran the drill, and stated that in "honor" of Easley's and Bueller's "deaths" that the squad would have to perform more drills.
On April 5, 2192, Bueller and the rest of Fox Platoon stationed on The Benedict left Earth on their eighteen month retrieval mission to bring back a specimen for the Terran Government. Unknown to the mission's commander; Sergant Wilks smuggled a stowaway on board before lift off and due to Colonel Stephens's unfamiliarity of the Marines under his command, he was unable to pic out the stowaway. Unlike their commander, Bueller and the rest of the Marines were able to pick her out due to the platoon being well acquainted with each other. Bueller was attracted to the young woman and soon would make attempts at getting close to her.
Hostage and Rescue Attempt
The young woman, who Bueller found out was named Billie, started to talk with her and would go after his fellow Marines if they insisted that she was brought on to be Wilks's companion on board. Billie; surprised by Mitch's actions, would tell him that nothing was going on between her and Wilks and eventually returning his advances. Wilks would later try to break up the budding romance between Bueller and Billie by overriding his feelings with his programming to obey a superior officer's orders.
Billie and Bueller continued to pursue their relationship regardless of Wilks's protest. Eventually, the two snuck off to a storage area and became intimate. Shortly after that, an alarm went off and Bueller rushed off to arm himself telling Billie to stay hidden. Bueller made his way to the armory with the rest of the Marines only to find that their carbines were sabotaged and were now unarmed. Bueller was captured in the ensuing fight on board and was taken hostage by the pirate forces. Bueller and the rest of the captured Marines were suited up in combat gear and loaded onto a dropship and sent to the surface of the planet's surface.
When Bueller and the others made it planetside, the pirates set the Marines near a hive to be used as hosts for more xenomorphs to be used by the pirate's employer. As the Marines of Squad One moved towards the entrance of the hive, the combat androids were ambushed in their air pods by an indegnous flying species taking out several air pods and grounding one, which an android managed to escape. The android made his way to the hive entrance to be greeted by Bueller and his squad. The squad disarmed the hostage with Blake getting his Plasma Rifle and Bueller taking the pistol.
The squad then left the hive and proceeded to acquire more weapons arming the rest of the squad by taking out more air pods and sniping grounded androids. Bueller managed to figure out that their coms where hacked by the enemy ordered the squad to head south, but then gave a coded order to head north to the dropship. The android hostage not understanding the order, headed south and was gunned down by friendly fire. With Ramirez on point; the squad was getting close to the dropship. Ramirez decided to scout ahead and secure the dropship; little did the Marines know that the pirates rigged the dropship with a timed explosive which went off and took Ramirez in the explosion.
The squad then received a transmission from Sergent Wilks, letting them know that the pirates on the Benedict have been delt with. Overjoyed that Billie was alive, Bueller was excited until the Marines received a panicked transmission from one of the crew. The panicked man was calling out for a rescue since his position was being overran by the xenomorphs. Bueller and the other Marines, following their directives that no harm could come to humans by inaction started to head to the hive to last known coordinates in the hive. Apologizing to Billie as he set out Mitch told her it was something that they had to do.
The squad made their way back into the hive and noticed that the xenomorphs were on them in waves as they made their way into the hive. In the first wave the squad lost Chin and Smith to the creatures. Leaving only himself,Blake and Mbutu; Bueller and the others pressed on. Another wave of the creatures struck with one of the creatures barreling into Mbutu, pinning her down before it's head was vaporized. Unfortunately for Mbutu, the creature's acidic blood doused her face, and the Marine opened her mouth to scream to get a mouthful of the acid. Bueller, doing the only humane thing he could, shot Mbutu in the head to end her suffering.
Secret Revealed and Return to Earth
Eventually Bueller and Blake made it to the hatchery in the hive and were able to find four of the crew members cocooned. When the Marines went to inspect the four they found that two of the three men and the woman were already dead from the chestbursters. Bueller and Blake released the last crew member, whose egg hadn't hatched yet. As the man was freed, Wilks and Billie landed in the spare dropship to evacuate the planet of the survivors. Happy to be leaving and to be with Billie again Bueller didn't notice the xenomorph drone that snuck up behind him. The creature then bisected Bueller at the waist revealing to Billie his secret: that he was an android. The dropship gave cover fire as Blake carried Bueller's upper half to the dropship.
After leaving Earth in the cargo ship the American, Bueller, still damaged, took up a spot on the bridge, presumably doing general tasks whilst Wilks monitored the last comms from the infested Earth. He stayed up there and provided support while Wilks and Billie went to investigate the cargo hold, which had been damaged by Xenomorphs which were being shipped in secret to General Spears' military base. Bueller played a key part, closing a hull breach (caused by a Xenomorph's acid), opening an airlock to sweep the remaining two creatures into space, and whilst Billie was being chased by the last surviving Xenomorph outside the ship he activated the engines manually, incinerating the creature and saving Billie.
As they arrived at Spears' base, Wilks and Billie were detained, and Bueller, technically being military property, was taken to an android maintenance bay, where he stays for most of the ordeal. Here, he deals with the duality of his existence; being an android, and yet having human feelings and emotions and his relationship with Billie, who was starting to reciprocate.
After the Xenomorph outbreak, Bueller escapes the bay in the chaos, deciding that he needs to help Billie survive. He crawls through the base to an auxiliary comms room, noting as he does that the creatures ignore him due to his synthetic nature. He once again monitors Billie and Wilks' progress through the base and provides support by closing a pressure seal just as the Xenomorphs break through, eventually seeing the two through to Spears' ship just before it takes off.
In the end, he is shown still alive and functioning in the Xenomorph-filled base, sending a message to Wilks and Billie. He mentions that the base has been completely taken over, and that he was trying to make sense of the relationship between him and Billie, but realizing that there was no sense to it; it "just happened-- random, unpredictable-- like life". He expresses his love for Billie one last time, and, shedding tears, asked for her forgiveness just as the transmission was cut. Billie solemnly reflects that the scientists failed when they made Bueller; he was not human, but better.
Behind the Scenes
In the original comics in which he appeared, Bueller was named Butler. However, for the novel Aliens: Earth Hive, an adaptation of the comic series Aliens: Outbreak, the character's name was changed. The same fate befell several other characters (notably Corporal Wilks and Billie). However, while the other individuals' identities were changed to avoid conflict with events shown in the newly-released film Alien3, the reason for changing Bueller's name is not clear.