This happened about a year ago. I was getting a massage and got to the part were you turn over onto your back. I had an erection, but this was no big deal because this girl drapes you with a pretty heavy blanket so it didn't really show. But, right then another girl comes in, apologizes profusely for disturbing us, explaining that she is just about to start her shift but needs to borrow something.
My girl hands her what she needs and the other girl reaches acrosss me to take whatever, and in the process her watch or bracelet cathes on the blanket and pulls it off of me.
Now the apologies really start flying, until she sees the state I'm in, at which point she chokes back a laugh and continues to apologize, all the while wrestling to get untangled from the blanket.
She finally does extract herself, tosses the blanket on top of me in a heap and sort of laughs/apologizes one more time. My girl straightens out the blanket and trys to go on like nothings happened. Meanwhile we hear gales of laughter coming from the reception area, which makes my girl laugh, apologize, laugh, etc.
the whole thing probably lasted two minutes, but it seemed like hours.