Very serious
The bra thing started because I few of the girls had older sisters. One family was bra shopping for the preteen when the preschooler started crying because she wasn't included. The only way the mom could stop the crying was to buy the 4 year old a bra.
The first thing she did came to school wearing it was to pull up her shirt and show the whole class. Of course all the other girls wanted bras. A few idiot parents gave in.
The girl that started it has been getting her nails done since she was 5. She's is in the 4th grade now. I saw her last week and her nails look better than mine.
The thong kid

She's constantly running around the building showing off the sexy outfits her mom buys for her. About four months ago she came into my room to show me the lastest outfit.
Child: "Ms.XXX look what my mom bought me, isn't it SEXY" Yes she used
the word sexy.
Me: "How old are you now?"
Child: "10"
Me" "10 year olds aren't suppose to be sexy."
That was the last outfit I saw.