This was an episode of Howard Stern in 1998 that I remember. Tickling wasn’t a central part of it so I don’t know if it even ever got clipped and shared onhere, but it’s the October 28 episode “Karen gets a breast exam”. It happens around 11 minutes and 45 seconds in, Howard is giving the woman a breast exam, and Robin reminds him that he needs to go under her arm. At least for me, when she hears that, her face registers nervousness, like she knows that it’s gonna tickle, and sure enough she gets ticklish and Howard tickles a little under her arm. I tried to post it on YouTube, but because there’s actual nudity it does not allow it.
https://archive.org/details/1998.03.11-blockbuster-awards-e
https://archive.org/details/1998.03.11-blockbuster-awards-e
