Neither. They’re so closely synonymous to each other that I saw little difference between them. I did not watch their cartoon very much at all, and in fact, the only reason I tuned in at all was that there was a man in my unit to whom everyone referred as “Beavis” on some occasions and as “Butthead” on others. Being about ten years older than they were, and being their Sergeant, I was unfamiliar with their pop culture. After lots of prodding, I finally yet reluctantly tuned in to see what all the hubbub was about, and after watching only an episode or two, I had to agree: he acted a lot like the two characters. I did not, however, become enamored with watching the show.
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