"Cornholio" claims that he is from various locations in Latin America. He has stated on one occasion that he is from Nicaragua and also claims that his home is in Lake Titicaca (with the word providing comedy for Beavis, because of its combination of the slang words titty for breasts and caca for feces), which is in reality located between Peru and Bolivia. He states his mission in life is to find "TP" (toilet paper) for his "bunghole", as his "people" are "without bungholes," or, in an apparent contradiction, that his people have "but one bunghole." This apparent contradiction is typical of the nonsense he frequently spouts: at other times he claims he himself is a bunghole, that he has no bunghole, that he has a portfolio in his bunghole, that he is a gringo, or calls upon "the Almighty Bunghole" (either referring to himself or his supposed god), or that he is the envoy or guardian of the Almighty Bunghole. He has also said: "You can take me, but you cannot take my bunghole! For I have no bunghole." He has also expressed an interest in "oleo" (oil), as well as "Roleos" regarding to spanish word "rollo" a short name used for "rollo de papel" which can be translated to "paper roll" and it means "TP" (toilet paper) for some Latin American people. He has also expressed interest in "Aqua", presumably because it rhymes with Nicaragua. "Nicaraqua" was the word that caused his first transformation, after which he paced around Van Driessens classroom chanting about "Aqua for my bunghole".
Cornholio is a very different personality to Beavis in one particular aspect: while Beavis is somewhat shy and prone to mumble, Cornholio is extremely forceful and loud. If anyone challenges him, he demands to know "Are you threatening me?", and on many occasions he has warned "unbelievers" of the "wrath" of his bunghole. Although generally he means no harm, he respects no boundaries or property rights, roaming wherever he wishes on his quest, frequently screaming at those he meets and terrifying them into submission. He is one of the few characters that actually sings (apart from the teacher Mr. Van Driessen), but his singing is off-key, and he sings only about either his bunghole, or the almighty bunghole.
Cornholio is also a pervert to some degree: he has repeatedly asked if anybody wanted to see his bunghole; he once went into a girls' bathroom, demanding anybody in there to "come out with [their] pants down"; and in Beavis and Butt-Head Do America he went into Mr. Anderson's camper to "whack off" over a picture of Dallas Grimes.
Beavis seems to retain no memories of events after he returns to "normal", on one occasion seemingly apologizing to Principal McVicker for having caused a problem. This indicates that Beavis suffers from Dissociative Identity Disorder. However, sometimes the two personalities collide: as Cornholio, Beavis can sometimes be heard muttering in his normal voice, usually before the phase has finished. Beavis also seems to do impressions of Cornholio, although this may just be what he does normally.
Beavis's transformations into Cornholio have been exploited by perceptive characters, most notably a coffee-bar owner who saw how many customers were coming to listen to Cornholio's "poetry" after Beavis became wired on "crappuccino". When the caffeine wore off and Beavis began to slow down, the bar owner simply filled him full of coffee again and Cornholio returned.
The name "Cornholio" is a reference to the anus, which is sometimes called the "cornhole"; the traditional meaning of "bunghole" is a hole in a liquor barrel or keg. This traditional meaning is explored somewhat in the series.
Cornholio first apparently surfaced in the episode Generation in Crisis, in a scene where Beavis amuses Butt-Head by pulling his shirt over his head and saying "I am the Great Cornholio, I come from Lake Titicaca!" in a humorous pseudo-Spanish accent. In scripting terms, this was merely Beavis "goofing around", but the moment proved popular enough to warrant making Cornholio a character in his own right. In the same episode, both Beavis and Butt-head pull their shirts over their heads and act like idiots (to a greater degree); in this case, neither Beavis nor Butt-Head refer to bungholes, T.P. or any other Cornholio obsession, indicating that they do not think they are Cornholio-esque characters at this point but are simply playing. In later episodes, where Cornholio actually appears, Butt-Head probably doesn't realize Beavis has multiple personality disorder, and assumes that Beavis is just playing.
Cornholio returned in Buttniks, in which the duo visit a beatnik coffeehouse. Beavis transforms after drinking large quantities of cappuccino (which he jokingly refers to as "crappuccino"). This time, his insane jabbering and nonsensical threats are interpreted as deep, spiritual poetry by the club's denizens. In the Halloween special Bungholio: Lord of the Harvest, Beavis transforms after eating Mr. Anderson's entire bowl of Halloween candy and begins wandering Highland, terrifying other trick-or-treaters into surrendering their candy to him. During the course of his wanderings, he does indeed find some toilet paper, though this does not cause him to revert to normal. He also has an encounter with Todd, but after Cornholio warns him to not "Underestimate the power of the Almighty Bunghole", Todd backs off and goes after Butt-head instead. In Vaya Con Cornholio, Cornholio surfaces at Burger World after Beavis drinks their entire supply of Volt Cola (a parody of Jolt Cola, which was promoted as having all the sugar and twice the caffeine of other soft drinks at a time when most manufacturers were reducing or eliminating both) and other sodas; he is subsequently interrogated by the INS and, after he insists he is from Lake Titicaca in Nicaragua, they deport him to (they believe) his native Mexico. Once there, Cornholio believes he has arrived in Nicaragua and declares that he will "take this land for my bunghole!" It is not known how he was able to return to Highland, but he is back home in the next episode (it should be noted that Beavis and Butthead has a rather loose continuity).
In an interview for the Mike Judge Collection of Beavis and Butt-head episodes, creator Mike Judge said that he had to be careful not to overuse the Cornholio character.
Later in the movie, the same old lady gives Beavis the same caffeine pills (thinking they are Xanax tablets). Later, while on a tour of the White House, he transforms when a guide mentions Pierre L'Enfant. During the course of his wanderings, he wanders into the Oval Office and calls Strategic Air Command, almost triggering World War III, before confronting a painting of Richard Nixon in his famous "V for Victory" pose, to which he utters his trademark "Are you threatening me?". He later sees Mr. Anderson's camper, and after being triggered by a picture of Dallas Grimes, he decides to go in and "whack off". An embarrassing moment ensues when Mr. Anderson sees his camper rocking and making strange noises, and he goes in and catches Beavis with his pants quite literally down. Later, after getting thrown out of the trailer, whilst surrounded by the ATF, Cornholio takes on an almost religious guise spouting such phrases as: "You will cooperate with my bunghole. For there is but one bunghole - the Almighty bunghole" and "You must bow down to the Almighty bunghole." He also starts chanting, in a vaguely Eastern way, saying things like "bungholiooooo". In the same scene, Cornholio also says things like "I have no bunghole". Cornholio shows confusion with his own circumstances, saying, in his normal voice, "Why does everybody want to see my schlong?", after the ATF agents repeatedly ask to see "the unit", referring to the container of genetically enhanced supergerms hidden in his pants by Dallas Grimes. He reverts to normal at the film's climax, surrounded by SWAT teams and soldiers, unaware as to how he arrived on Pennsylvania Avenue.
Beavis also occasionally speaks with Cornholio's voice during music video reviews. On one occasion, he claimed there was a "Spanish dude" living inside his head, who told him to pull down his pants and "spank his monkey".
In the video game Beavis & Butt-Head: Little Thingies it is possible to trigger Cornholio in the "Wrecked 'Em Ball" segment, where Beavis must catch snacks thrown by Butt-Head from a condemned building while avoiding falling debris. When Beavis consumes enough snacks he will transform into Cornholio, essentially making him invulnerable for a brief period of time.