I swear this actually happened in a class I was in about three months ago.
It was a small yoga class -- I was the only guy, a female instructor and four or five female "classmates" of mine.
Frequently in yoga, instructors will walk around and gently push someone into better positioning, or sometimes give little mini-massages.
Well one of the other students was bent over in I believe a "downward-facing dog" pose, or something similar, and the instructor came and kind of started massaging her sides from behind her -- the girl started laughing uncontrollably, but kept her position. The best part was that the instructor didn't immediately stop the "massage" -- not because she was turned on by the tickling in my opinion, but simply because she assumed the reaction might have been more about the surprise of being touched there, and that the girl would likely relax into within a few seconds.
But she kept laughing. So after about five seconds, the teacher stopped.
It was one of my better moments in yoga class. 🙂