Though I never really had an issue with getting my rectal temperature taken, even though when younger I was agreeable to a rectal when my Mom asked during my illness if I wanted it in my mouth or "back side". I opted for the rectal method and she did it.
A few years later when we moved I was seen by a new doctor, a G.P. in a first time examination. I was 16 at the time. This young woman was quite thorough in her examination of me. She had me strip to my underpants, don an open back gown.
I was weighed, height checked, returned to the table, my heart and lungs listened to, then my blood pressure taken.
After that I was instructed to lay on my stomach. I looked at my Mom, and she sort of looked like, Well, hon, I'm not sure why...but.
I heard the draw open on the cabinet, watched the doctor remove a small jar of Vaseline, and a thermometer which she rapidly shook down, held up and read. Then she walked over to me, grabbed the waistband of my underpants and lowered them, and within seconds was spreading my cheeks, and slowly inserting the thermometer into my rectum. After three minutes or so, the thermometer removed and my underpants pulled back up by the doctor, and the rest of the exam continued.
I got a clean bill of health. The doctor said she was grateful I didn't fuss when my rectal temperature was taken, and cooperative patients made her job that much easier.
After returning home, my Mom said she was really surprised that the doctor had taken my temperature rectally, but said it was not her place to interfere with the doctor's decision. I reminded her that years earlier she'd given me the choice, and I opted for the rectal route.
"Well", she replied, "if you're OK with that ,then that's fine with me."