Hello, Miss Poopy Pants

I see these kinds of pants quite often here and I always stare. This time I took a photo, although it really doesn't do it justice. The girl on the left is wearing what I like to call "poopy pants," because that's what they look like! They are pants that fall down beneath the crotch for about a foot and droop. I don't understand how girls walk in these but somehow they manage. I'd really like to know if girls are wearing these in the U.S. (?)