This won't be graphic, so don't worry.
Last night, I was laying back on the couch watching TV, when I suddenly got the urge to break wind. I was by myself, so I did, and I didn't feel even the slightest urge to poop, nor did I force it, I just farted. It felt completely normal, and I honestly didn't feel anything unusual about it.
But perhaps ten seconds later, I realised that I felt a certain warm, wet feeling around my bum. I was wearing black satin boxer shorts, and I reached under and rubbed them, and was stunned to discover a wet patch!
I quickly got up and went to the toilet, where I discovered a wet spot the size of an ashtray on the back of my shorts. Wiping myself, I discovered that my bottom was very wet indeed.
I had the runs, and sitting on the toilet, I pushed, and it came out like almost pure water.
Oh no! I'd had an accident! A real one! And I'd pooped my pants!
I had to think fast. My family had all seen my walking around in just my boxers, and would wonder why I'd changed them. But I remembered I had a second pair almost identical.
That's where my little mode kicked in. From then on, It was just like I was a kid again, and I was trying to hide the evidence of my wet pants. It had happened a few times as a kid, wet, not messy, but the mindset was identical. I had to clean myself up, get changed, and check for damage, and hide my pants without anybody working out what I'd done.
I wiped myself clean as best I possibly could, washed my hands, and hid my soiled pants underneath some laundry in the bathroom. I found my clean matching pants and put them on.
Then, I went back to look at the couch, (tan suede) and to my horror found two small wet spots about half inch across each. I wet some paper towels, and vigorously wiped them off. Thankfully it's an old couch, and the dogs sleep on it as well, so it's already got a few stains on it.
I told my wife I'd spilled my wine on it, and was cleaning it up.
After that, I announced that I wanted a shower, so I went back, scrubbed my dirty ones, and hid them in my wardrobe before having a shower.
The entire time I was in "little mode," running around furtively like a nervous little boy trying to hide what he'd done.
The entire experience was rather nerve racking, but it was an intensely regressive one at the same time.