Longshot but I am looking for an old clip which featured a woman on a couch being tickled by two other women while trying to not react. The clip was named dontlaugh.rm
I think I know the one you mean, she sits there whilst these two women are saying, "she's not going to laugh" whilst they tickle her feet after taking her socks off. At one point she does giggle, which she claims was for another reason.
I always wondered what the conclusion to that clip was, since they then tell her to lie down, presumably so they can try her upperbody..
What you described is correct, that is the clip I am looking for. If you happen to find it please share it here. If I can find it, I will share it here also.