I've never had the offer to spar a total martial arts loser even though there are a shitload at my school, the only explanations I can find for this are bad luck and my being freakishly tall.
Sadly, this was with a friend of mine, too on the nerdy side, but we got along training with each other (conditioning). TKD Black belt and competitor (not of Olympic caliber, but much of his school was I believe), but a smaller guy, maybe 150 tops, with me closer to 220, obviously not even match. I had been doing BJJ maybe 3 months. Now this guy is athletic as all hell, but all he can do is kick (faster than I can punch). Anyway, another friend and I are rolling and he's in the campus matroom with us messing around and I convince him to spar with me. We have no gloves, mouthpieces or cups or anything, but I say go full on buddy. I refused to punch, so it took awhile, but I checked a kick, clinched, crappy suplex=>side-mount, mount, armbar. I felt bad about it and still haven't really convinced the guy to fight for real. After that night he literally retreated to his room and got addicted to video games; we haven't seen him at archery or MA since. We'll see.