I have been over on the enema side of things, and just found this thread.
There was a group called FEB, for Frank E. Ball, I think this goes back to the 70s. Anyway I learned about marshmallows there.
It went like this, buy a bag or two, open the bag and let them dry out and become firm. Now take a bowl of warm water and immerse one at a time until they become slippery. Then up your buttthey go. Everything will be fine, then all of a sudden there will be no holding back, no stopping them, no getting to the toilet in time, they are going to explode out of your ass, you are out of control.
About the same time there was this fellow, Tom S. from Schenectady, NY who was trolling for young guys who liked, or in my case, loved enemas. They had some rather interesting group sex play, including putting a fellow in a sling on a cold winters day in upstate New York and filling him with marshmallows. About that time a bunch of straight guys on snowmobiles wander by, see what is going on, including enema bags hanging from trees... well you have never seen a group make a 180 and disappear as fast.
But having been on the sidelines, and even though I am straight, if enemas are involved lines are happily crossed. This idea of out-of-control shitting really turned me on. So shortly thereafter I buy a bag of marshmallows and convince my wife to fill me up. And it is true, you get in so many, about a dozen or so, and there in no holding back.
Because my wife, who happily did enemas, had a problem with nausea from soap suds enemas, she opted not to try it, but we did have a friend, a nursing professor, who loved anything and everything up her butt.
So Margo became our victim, and you have to understand Margo liked messy. Same thing, about a dozen and she cut loose. Because she liked things messy she had done as she would do for enema sessions, held back for a day or two.
This is a memory from about 40 years ago, but I have to say there were used marshmellows and shit everywhere. Then Margo wanted enema after enema. I mean she just went nuts with orgasm after orgasm. It is intense!
Fast forward to about 10 years ago when I shot a marshmallow video with Bridget Harrington, same thing, no holding back, when you gotta go you gotta go. The night spent following the play was intense, too. The following day was her beginning her transition from Bridget Harrington to Lee Harrington, it was her last female experience.
So far I have not given Lee an enema, but I got to enema, marshmallow and do fruit insertions with Bridget.