No characters from one show have ever appeared on the other, although the Beavis and Butt-Head character Tom Anderson strongly resembles Hank Hill. See the entry above for more information. These are some similarities/parallels/etc. between the two shows:



-Stewart Dooley's voice is very similar to that of Butt-Head (although he doesn't use Butt-Head's obnoxious giggling after speaking each sentence.)



-Gary Kasner has a submarine tattoo on his chest. So did Coach Buzzcut on Beavis and Butt-Head.



-The Beavis and Butt-Head episode Temporary Insantity features a female real estate office employee who strongly resembles Peggy Hill, both in appearance and personality.



-The Beavis and Butt-Head episode The Beaverly Butt-Billies features a sewage company employee who speaks in a voice identical to that of King of the Hill's Joe Jack.



-Bobby shares many characteristics with Beavis and Butt-Head's Stewart - both are chubby and "nerdy" compared to their peers. While Stewart is clearly the more intelligent of the two in an "academic" way, Bobby has more self confidence and common sense.



-Many Beavis and Butt-Head episodes feature a morbidly-obese woman living in a trailer, with one of her constant companions being a man wearing nothing but pink underwear, a cap, and always smoking a cigarette. This character is believed to be a prototype for Dale Gribble.



-While not any kind of direct reference, the voice of Boomhauer is based on that of an irate viewer that called Mike Judge to complain about the content of Beavis and Butt-Head.



-Toby Huss voiced one of the men who steal Beavis and Butt-Head's TV in the theatrical movie. Huss later became a regular voice actor on King of the Hill, voicing Kahn, Cotton, and many others.



-Beavis and Butt-Head once watched auto racing, calling it a "bunch of dumbasses going around in circles", but called it "the greatest show in the history of television" the second someone crashed and went up in flames. Bobby and Joseph had the exact same reaction to watching auto racing - wondering what the appeal was, but going insane with happiness upon seeing a crash.



-The late Robert Stack performed a guest voice on both series. Edit