(correct me if i get the names wrong; i don't watch the show regularly)
i remember seeing an episode where this guy was hanging out with the guys and he and Kate didn't get along very well, but by the end of the episode they fall in love. At the end the gang is shooting pool in the back yard and the guy asks "is there anything special i should know about Kate now that we're going out?" Louis replies, "if she says 'stop tickling', stop tickling; she'll pee her pants." Kate responds "once! and i was only 23!"
I know it's not an actual tickling scene, but i thought it was funny.