I've had this happen to me a few times, both as receiver and watcher. Here's one for now.
When I was 15 (in 2000) I was on vacation with my family, visiting a school-friend of my mother who had a house in France. Well, as it happened, I got a relatively minor flu kind of out of nowhere, just chills and some fever, nothing really bothersome. When we traveled, the only thermometer we packed was an old fashioned glass one from when I was a toddler, so it was rectal temps to make sure I didn't have a high fever. My mom usually made sure it was just us two, for the sake of privacy.
Anyway, one evening during this flu of mine, my mom comes in to take my temperature but can't seem to find the thermometer. So she does the obvious, and asks her friend, Claire, if she's got one we can borrow. Claire enters with one in short order, and it's also a rectal thermometer. That by itself wouldn't have bothered me, but the two of them promptly start a conversation, during which mom is going through the motions, shaking it down, and sitting by my side on the edge of the bed.
At this point I'm already kind of anxious about what's going to happen, and then mom takes my waistband and lowers my pyjamas to my thighs with Claire still in the room, the two of them stull chatting. I'm too embarrassed to complain, and mom gently spreads my cheeks and smoothly slips the bulb in my butt, just as if it were just us. I was blushing so hard that I hid my face in my pillow, but neither of them actually talked about my predicament or seemed overly concerned that I was in plain view, thermometer nestled snugly in my bottom.
Four minutes later, mom reached over to slide it out and read my temperature, so I quickly pull up my pyjamas and try to hide my face some more. Claire casually mentions that she's got some paracetamol suppositories (she has three daughters, my guess was those were usually meant for them) and she and my mother exit, thinking nothing of what just happened.
A minute or so later I calmed myself down knowing that Claire took her daughters' temperatures that way too, but in the moment I was so embarrassed!
(Ended up actually getting some if those suppositories)