I guess it's kind of odd that I don't remember any insertions when I was young. I'm sure I had rectal temperatures when I was young, and know I had suppositories and enemas, but what I remember was the cramping and expulsion after the insertion/injection. I guess that's a good thing, and means the insertion was done carefully and it was not a big deal.
I remember getting a suppository from my grandma at about 8-10, but again don't remember her finger or the suppository going in. I remember the event for a couple of reasons. She asked in a way that made me realize I could say no, I was mature enough to realize I needed something so said "yes," and she used gloves and lube.
I remember my first DRE. Dreaded the thought of one since puberty, pretty much every time I was at the doctors. Boys will talk sometimes, and a couple of times a group I was with launched into the awful, embarrassing things that happen in medicine. I had a few welcome misses, including the time I smashed up a bone and had to have it surgically put back together right as puberty was starting. Big relief there - not only did I not get a rectal temperature or enema at the hospital, I was even able to wear my underwear (the little mercies count big).
Of course narcotics back me up big time, but that was later at home. I later had to go to the doctor for pelvic pain/urinary issues but counted myself lucky that I was able to get out of a DRE there (I played my PCP and the urologist off against each other- they both thought the other had done it). Of course that meant I had to put up with the issue for a while longer until I went back with worse pain. Then they did it and - guess what!- no big deal.
My doctor was gentle and has a great patient skills. Was prescribed some antibiotics and things got better (I had forgotten that semen was normally very white). Of course between that and the IBS I got tight pelvic floor muscles and developing CPPS, which lead to another DRE for muscle tone evaluation and several rounds of internal trigger point therapy. Fortunately the PT was also gentle and had good bedside manners, so I think I'm now pretty desensitized to DREs.
My first with my wife was something I asked for. We didn't use enough lube and she didn't get deep enough to catch my prostate, but it still felt great. Anal play fell by the wayside when things started hurting down there. I'm hoping to start back up now that things feel better.