Mike Judge got the name Butt-Head from his university days, when he knew a couple of kids who had the nicknames 'Iron Butt' and 'Butt-Head'. Some of the mispronunciations of Butt-Head's name by adults include Buffcoat, Headbutt, Butthole, Butter-head, Buttbrain, Tangpode, Nuthead and Bob-head. Senator Ernest Hollings actually first used the name 'Buffcoat' on the floor of the U.S. Senate — an incident believed to have inspired incidents of mispronunciation of the title characters' names.
Butt-Head seems to be the lazier of the two. He never seems react to things unless they catch his attention, in which case he describes them as 'cool'. Beavis, on the other hand, always has some kind of reaction, although his actions predictably end with bad results.
Butt-Head wears dental braces and has squinted eyes. His top gums are often exposed and he speaks nasally with a deep voice and a slight lisp, repeatedly punctuating his speech with his trademark laugh (Uh huh huh huh). He is usually shown wearing an AC/DC t-shirt. However, he is seen wearing a Metallica shirt for a few seconds in Crisis Line. In merchandising appearances, his shirt displays the word 'Skull', to avoid licensing issues. He is also known to fashion his hair with his own phlegm as if it were hair gel as seen in rare footage during the music video segments.
Though Butt-Head is physically weak to the point of being unable to lift a bar without weights (Buff n' Stuff), he is still somewhat stronger than Beavis. He dominates the majority of fights they are involved in. In some episodes such as TV Violence and Special Delivery Beavis does fight back against him.
Butt-Head's parents are not seen, except for in Beavis and Butt-Head Do America. His dad is shown as a former Mötley Crüe roadie voiced by David Letterman. The two part company before they make the rather obvious connection. It is implied that Butt-Head's parents are divorced (or perhaps never married); in True Crime the two were watching the music video for Grace Jones's "Demolition Man". Beavis claimed the video was scary and asked Butt-Head if he could spend the night at his house, to which he answered "I'll ask my mom's boyfriend when he gets home." However, because the two have already practically lived together for the entirety of the show without any parents being seen, how seriously this should be taken is debatable.
On many occasions, Butt-head is depicted as being abusive towards Beavis, usually slapping or insulting him. Most of the time, he receives no retaliation, with some exceptions (Murder Site, Nose Bleed, Prank Call, and some music videos when Beavis kicks him in the testicles). In several episodes Butt-Head shows no concern for Beavis, whether Beavis is being severely beaten (Teen Talk, Tired and Do America), abandoned (B&B vs The Vending Machine) or deported to Mexico (Vaya Con Cornholio). The feeling appears to be mutual, as seen in Water Safety when Butt-head nearly drowns in a pool and Beavis remains indifferent to Butt-Head's near-death experience, and in Choke when Butt-head chokes on a chicken nugget and Beavis takes his time attempting to help him as if it were nothing serious. Beavis tells the 9-1-1 operator "He's not really my friend". When Butt-head is in a situation when he may need Beavis' help, Beavis' reluctance to help him may be due to a failure to realize that Butt-head needs help. In Choke, when Butt-head tries to demonstrate that he is choking Beavis says "I hate this stupid game", as if Butt-head were playing a game of charades. When Beavis gets a nosebleed (caused by Butt-head punching him in the face), Butt-Head "tries" to help him, resulting in Beavis losing a great deal of blood (Nosebleed). In The Final Judgement of Beavis, after Beavis knocks himself out by crashing into a wall of the house, Butt-Head revives him by dumping a bucket of cold water on him.
The two characters spend most of their time with each other. They share the same occupation, and usually compliment each other when one makes any sort of endeavor, especially if it involves their life-long goal to 'score with chicks'.
Mr. Van Driessen is alone among teachers at Highland High in that he sees potential in the duo and he tries to reach out to them and encourage them. He makes several attempts to teach them life lessons, to no avail. Conversely, Coach Buzzcut takes every opportunity to embarrass them, exposing both their stupidity and their lack of masculinity. Principal McVicker has no idea what to do with them, as every attempt he makes to instill discipline in them fails miserably.