Vault 101's resident bully, Butch masks his fear and sense of inadequacy regarding his alcoholic mother and the lack of a father figure by becoming boorish and overbearing. This masking of his shortfalls has stunted his secret desire to become a hair dresser.
During their formative years, the Tunnel Snakes harassed other students in the Vault, even being bold enough to taunt the Overseer's daughter Amata Almodovar. Due to an agreement with the Overseer, the Tunnel Snakes are largely left to their own devices, and few stand in their way.
Growing Up Fast: On July 13, 2268, Butch attends the tenth birthday party of the Lone Wanderer. Butch mentions to other boys that he wouldn't have come to the party if his mother didn't insist he should attend. During the party, Butch holds a small meeting with his friends to toss around ideas for a name for their gang. He picks on the Lone Wanderer in attempt to get a sweetroll, which can end with him starting a fight.
Future Imperfect: On August 3, 2274, Butch and his friends are verbally and sexually harassing Amata. At this point you can choose to fight Butch and his gang, tell off Amata about her weight, tell Butch that Amata's father will punish them, convince Wally to make the others leave with him by telling him that he's "just a follower," or ignore them and continue to the classroom. Later, after the G.O.A.T. examination, the teacher informs Butch that his G.O.A.T. exam answers determined him to be a hairdresser, something that amuses the long-suffering teacher and outrages Butch, who proclaims angrily, "I'm a barber, not a hairdresser!" He walks out of the room infuriated and meets his friends outside the classroom.
Escape!: After James's escape, the Vault becomes infested by radroaches, and Butch's mother, Ellen DeLoria, is attacked by the insects. Butch asks the Lone Wanderer to help save her. The player can choose to help Butch and his mom or leave them to their own demise. Butch can also be convinced to save his mother himself, either by giving him a weapon, or passing a speech check. Helping his mother earns you a Tunnel Snake outfit. Another option (if the player's Charisma and/or speech skills are sufficient) is to further torment Butch about his fear of radroaches via a successful speech check, causing him to flee and abandon his mother. However, if you choose this option, Butch will be found dead as you go upstairs to the atrium; the cause of his death unclear. You can also choose to kill Butch outright, making him unavailable as your companion later in the game.
Trouble on the Homefront: During Vault 101's factional crisis, Butch sides with Amata's rebels. He will be upset about your return due to all the problems you and your father's escape caused. Butch wishes to leave the Vault so he can make his own choices in life, and somewhat naively wants to start a new gang in the Wasteland. If asked about the events after your escape, he will mention Stanley's fears about the damage the Vault's systems sustained, and hints that permanent damage to the air filtration systems may force the Vault to be evacuated. Of course, if you killed Butch in Escape! he won't be in Vault 101.
Tunnel Snakes Forever: When you finish Trouble on the Homefront, make sure Butch is still alive and the Overseer has lost control (either by convincing him to step down, killing him, or sabotaging the Vault). Move to the Muddy Rudder, strike up a conversation, and you can convince him to join you in some adventuring - but only if your Karma is neutral. 
Butch is one of the two neutral followers in Fallout 3. Following the resolution of the crisis, Butch can be found in The Muddy Rudder in Rivet City. Once you have recruited Butch, he will not leave if your Karma goes below or above the neutral range, but if you are separated or if you fire Butch your Karma must return to neutral in order to recruit him again.
Butch is afraid of radroaches. He admits this to the Lone Wanderer if asked why he himself doesn't go into the room to rescue his mother from the roaches instead of asking somebody else to, yet can be induced to overcome this fear with a Speech check.
After becoming a companion in the Muddy Rudder, there is a chance of getting Butch's switchblade without killing him. Just ask to trade and it should be there. Also, if he is killed after he declines to be the player's follower, people in the Muddy Rudder won't attack you.
Snowflake of Underworld insists that he is a stylist rather than a barber, seemingly the opposite of what Butch claims to be after taking the G.O.A.T.
The male haircut, the "Tunnel Snake", is named after his gang and is worn by Butch himself.
Unlike all other followers, Butch must have at least 1 round of 10mm ammunition in his inventory to use his default weapon (the 10mm pistol). However, he will not actually use up ammunition when firing his default pistol.
Butch will occasionally mention needing some sunglasses while idle or walking around with the player. Even if the player places some sunglasses or the lucky shades in his inventory, he will wear them, but will still mention needing sunglasses.
In the Growing Up Fast quest, Butch can be heard discussing possible names for his future gang. Paul Hannon suggests the name "Vault Dwellers", which Butch calls out as stupid. This is a homage to the Vault Dweller, the original Fallout protagonist.
Despite wanting to form a gang, when trying to recruit him while having a current companion he will complain about "crowding".
After giving you the BB gun, your dad says he fixed the gun with a spring from Butch's switchblade.
If you try to recruit him with your Karma too low, you'll offer him to "rampage the wastes" with you, to which he'll graciously decline saying that "...you're too intense." further saying "Butch likes a little action, but you...you're a psycho!"
Butch and his gang are modeled after 1950s-style juvenile delinquents known as "Greasers", seen in movies like West Side Story, The Wild One, Rebel Without A Cause, as well as later "retro" movies and TV programs that hearken back to the same era.
Butch trying to steal the sweetroll is a direct reference to one of the character creation questionnaires of Elder Scrolls 1, 2 and 3, also made by Bethesda. The scenario is also referenced by a guard in Elder Scrolls V who asks: "Let me guess; someone stole your sweetroll."