Well, this actually happened to me today, and since I joined this forum today, I'll post it here, I guess.
So, like many people out there, I have the habit of singing in the shower. Now, I have a very pleasant baritone ( this opinion is not shared by the general public ) and the acoustics in the shower complement it nicely. Today, I was trying out "Sometimes You Can't Make It On Your Own", and I had just reached the part where he goes "And it's yoooooooooouuuuuuuu when I look in the mirror....." when, all of a sudden, by mistake, I knocked the shower faucet onto the "Cold water" setting. The ensuing gush of H2O which seemed to have been piped straight from some Alpine glacier allowed me to temporarily reach Bono-like heights of falsetto. I will never sing in the shower again. Well, atleast not for the next week.
Weird singing experiences, anyone?