I remember the first time I got one was from my mom when I was laying on the sofa sick. For some reason, all I remember is that I was already laying across her lap and she pulled down my pajama bottoms really quick and slipped it in. I screamed and cried and begged her to take it out. She said she couldn't because it was melting.
I also remember another time when I was a little bit older and I rolled off my bed and hit my head on the glass top of a night stand really hard. I woke up my parents screaming in pain. They came running in and when they figured out what had happened, they came back with a cold washcloth to put on my bleeding head.
Afterward, one of them left the room and went into the hallway bathroom. I heard the sink water running briefly and my mom came back with a blue/green sleeping suppository in her hand. I immediately freaked out and tried to get between the wall and my bed to protect my bottom.
She and my dad kept trying to console me saying "it's only a suppository" and "they give them to people in the hospital all the time, just rollover" and "it'll only take a second". I continued to protest loudly, but my mom ran over and pulled me by the arm out from between my bed and the wall and forced the suppository into me. I was so humiliated and angry. It only made it worse when she said "shhh, shhh, it's already melting, there's nothing you can do about it."
Then the next day, to add insult to injury, my dad was making fun of me at the breakfast table for throwing such a fit.
To this day though, I love the idea, and the occasional experience I've had with the forced suppository role play. Both giving and receiving. This has extended to other anal eroticism for me as well.