I've had an experience somewhat like that, from the other side. When I was around 10 years old, my classmate pounced on me and tickled me until I peed -- 15 minutes or so. I didn't cry in the standard sense of the word, but I definitely had tears in my eyes from laughing so hard.
I was helplessly ticklish back then (*wistful sigh*)... I was lying on my back, he was on top of me, mercilessly tickling my ribs, and all I could do was laugh and laugh, and try to squeeze his fingers with my arms -- didn't even have enough strength to try to tickle him back. At first I didn't want to beg him to stop, as my pride would not allow, and I was sure it would have no effect anyway. By the time I changed my mind, I had no air to spare for conversation: I was so far gone in silent laughter that making any sound at all was quite impossible, let alone uttering an intelligible word. So, I resigned myself to laughing it out until he got bored. Eventually I lost control of my bladder. Some time later I managed to sqeeze out the words "I peed myself"; I still remember feeling moderate surprise at the way my voice sounded while I was quaking with silent laughter -- very high pitch, slow, clear, almost uninterrupted. At that point he let me go.
I didn't like being tickled at the time, yet I didn't resent him for tickling me. I think I blamed it on myself for being so ticklish. Now it's one of my fondest childhood memories. *sigh* what I would give to laugh like that again...