It happened to me twice.
Once my mother caught me dressed up in some of her clothes and a nappy. I was 12 at the time.
I had stupidly been wandering around in our garden feeling the cool air under my skirt and revelling in the boldness of my actions when I heard a "What the hell are doing?" from behind me. She had come home early and was furious at her discovery. In shock and in tears, I was marched indoors and made to strip in front of her. I begged her to let me undress in the bathroom but she just shouted at me to "Get out of those clothes NOW!" To say she was even more horrified to discover I was wearing a nappy and frilly baby pants (real extra large ones still fitted at the time) underneath sent her into an incontrollable rage. Thankfully I hadn't used the nappy otherwise she may well have had a heart attack. Once I undressed, she grabbed all the clothes, nappy and baby pants, stormed out and locked me in my room for several hours.
We didn't speak for days afterwards but then she calmly sat me down, pulled the things I had been wearing out of a bag and asked me to explain why I had been wearing them. I said I didn't know why, I just wanted to see how it felt and I promised never to do it again. She said as long as I didn't no more would be said but if she ever caught me dressed up again she would tell my father and he would throw me out of the house. Needless to say I didn't do it again for a good long while after that but, as many of us know, the urges eventually came back and so did the dressing up. However, I made sure she never caught me again.
The second time was with a girlfriend who I had been with for over a year. I was 15 at the time. I was going through a particulary difficult hormonal time and feeling very girlish to the extent that I started to experiment with light make up when no other members of the family were around. On one such day I had been in make up for several hours (just a little foundation, very light eye shadow, just a hint of blusher and nearly worn off lippy) when my girlfrien called. Without thinking I invited her in and as soon as we kissed she asked me if I was wearing make-up? I must of blushed deep red because she said she was sorry and didn't meen to embarrass me. I made some pathetic excuse about wanting to cover up my acne which I'm sure she didn't buy but to her credit she didn't press me on the matter. We broke up shortly afterwards but it wasn't due to the make up.
Anyways - what about you?