I was potty trained around 2 years of age (according to my parents). They offered me toys in exchange for giving up diapers and I quit cold turkey. It was a couple years later (around 4) that my fascination for them rose. My older sister and I used to play "family" as kids, and I was usually her baby when we played. One day, we asked my mom if I could wear some diapers to look/feel more like a baby while we played. We still had plenty left over from when we were younger, and my mom surprisingly said yes, as long as we didn't actually use them.
I was playing diapered one day with my sister and realized that I had to pee very badly. I was enjoying our game so much that I pushed off the urge and continued to play instead. Finally, I felt like I was going to burst. I remember running to the bathroom - frantically trying to take off my diaper when it happened: I wet myself. I remember looking down, and watching my diaper fill with pee. I had been holding it for a long time, and I wet a lot. What surprised me the most though, was that this "baby diaper" held my whole wetting. Here I was, a young kid - technically too old to wear diapers, yet I just used one with no trouble. Even though I knew at the time what was happening was wrong, something about it felt so right. I can't place my finger on why, but ever since that experience, I've always felt comfort from diapers.
Eventually, my mom found out that day, and took my diaper away. She never let me or my sister play with or use the diapers again. I remember standing in the bathroom as my mom was drawing a bath - looking over at my used diaper that was rolled up on the bathroom counter. I felt incomplete, like something was missing. All the comfort, confidence, and freedom I felt wearing diapers seemed distant. It was from that day on that diapers became something special to me: a comfort that nothing else seems to fit.