A few years ago my doctor ordered a precautionary ultrasound of my upper right abdomen and ribcage to make sure I didn't have an issue with my gallbladder, as I was having some discomfort in that area at the time. If you don't know, the gel they use for that does a pretty good job of simultaneously helping the ultrasound probe glide across the skin, while also reducing sensitivity 🙂(). Even so, at one point the ultrasound tech put the probe back in contact with my skin a little high on the side of my ribcage while I was keeping my arm stretched above my head as instructed, and it tickled in a way that made me flinch. She responded with, "oh, sorry!" I took that opportunity to say, oh it's fine–I guess I'm just a little ticklish. I was hoping for another quick intentional tickle or something like that, but she just replied, "Oh, okay...Oh my god, some people are just so ticklish, I almost can't even get the imaging I need! It's crazy!" So while I didn't get more, I got some unexpected insight into the field that stuck in my imagination for quite some time.