While never having experienced enemas as a child, I did personally experience many a rectal temperatures, including seeing most of the ones received by my little sister.
Every single clinical rectal temperature was witnessed by our mother in a doctor’s office. I actually mostly loved everything about getting my temperature taken, (except for my mother being there). Although she never said much, it was extremely embarrassing to have the woman who bathed me and changed my diapers watching or partaking in the procedure.
In the beginning of my memories, I was over Mom’s lap as she held the thermometer after the nurse’s initial insertion. It wasn’t long until I was soloing face down while drooling on that crinkly white exam table paper with a thermometer protruding from my bottom. I much preferred the nurse who was usually a stranger to me, to help unbutton, remove my pants and lower my underwear, than to have my mother help in any way.
I had a babysitter who worked as a candy-striper, and was so into taking my temperature, that she could have used a gunslinger’s holster to keep that thermometer at her ready. She took my temp (at least once) every single time she babysat me, and I remember thoroughly enjoying it with little to no embarrassment because my mother wasn’t there.
So yes, between the sheer numbers of times my bottom got glassed as a child, and the humiliation of my mother watching or looking on during the clinic visits, I had no chance of not having a RT fetish. I blame mostly my mother for just being there.
As far as physical sensation goes, I’ve always enjoyed that part, because why wouldn’t you?
As an adult, the preparation and premeditation also adds to the endorphin kick that accompanies getting or giving a RT.