Why did I stop to read this?
A few thoughts from an old guy.
I think kids of that age (really, people of any age) like to emulate people they admire or look up to. As for giving the underwear away, I think it has been done a long time, typically by girls/ladies, trying to express their liking of somebody in a demonstrable way. Example, throwing underwear at Frank Sinatra, Elvis, the Beatles, Tom Jones (that is about as recent as I can think at the moment, LOL). The girls/ladies (g/l) throw them at these guys as an expression of liking them, and in throwing them, the g/l are in a sort saying they are willing or wanting to do something with these stars. However, (a big however), most (not all, but most) of these g/l would be stunned, mortified and horrified if any of those guys called the g/l on their 'offers'. The g/l are doing it to be cute, like stuffing a dollar bill (or whatever the right amount is) in the belt (or whatever the guy wears) of a Chippendale guy. It's sort of a fun thing, but if the Chip guy called the g/l on it, she would be speechless.
I think this may be similar to that. It comes across as an offer, but in a mostly playful, coy way. Trouble is when things move further.
I also think kids do (always have) emulate the stars and what they do. In '57, as an 13 year old, I had long sideburns, greased up hair, wore purple and pink pants with a t-shirt, a pack of Luckies rolled up my sleeve, like Elvis. Today the kids try to actlike the stars of today, in their dress, talk and actions. Always have, always will. And parents will always frown on much of it. Problem is, IMO, the envelope of what is permissable, in everything, keeps getting pushed further out. Language, dress, entertainment, morals. Always has, always will I am sure. Who knows what might be 30 years from now. If alive, I will be 90, probably won't care, LOL.
Have fun, moms and dads.
