I posted this sometime ago. It's undoubtedly the best mainstream tickling I ever saw:
Candid Camera
It must have been around 1983 when I saw the most terific instance of trapped foot-tickling I ever witnessed. I was watching Candid Camera with Alan Funt and Fanny Farmer. They did a sequence where Fanny stuck her stocking-covered leg through a hole in the hosiery counter of a department store. I think she was wearing dark colored (maybe black) sheer stockings. Her leg stuck straight up in the air beside two or three mannequin legs, all modeling various shades of stockings. As ladies came through the area and stroked the mannequins' legs (to test the feel of the hosiery) they eventually stroked Fanny's leg and she would let out a giggle and wiggle her toes. Of course, this freaked out all the ladies... which is the reason this skit was staged for Candid Camera in the first place. Occasionally Fanny just wiggled her toes and called out to passersby. (I guess there weren't all that many women who just needed to feel the hosiery before they chose a selection.)
The best part was the last person "caught" on camera. It was a middle-aged man who completely fell for the gag. He was probably trying to find some hose for his wife, so he was testing the feel of the stockings on the mannequins legs. When he got to Fanny's leg, she let out her standard giggle and wiggled her toes. He jumped back in surprise and looked around. It didn't take him five seconds to move back to the counter and stroke Fanny's leg again. When she giggled and wiggled her toes he moved his had up to stroke her heel. At first touch her giggle changed from a light hearted "gotcha" giggle to a "oh shit!" laugh. He proceeded to spider tickle the bottom of her foot. Now she was laughing and wiggling for real! This went on for thirty seconds or more - long enough that Alan Funt had to approach the man to tell him they were on Candid Camera.
This television episode really happened, and I would LOVE to get a copy of the show, if anyone has it.