It's well known that Blac Chyna, friend of Kim Kardashian, has had etensive plastic surgery. The list includes: butt implants, breast implants and a possible nose job. While there's not a before and after photo to illustrate the differences in her breast size and butt size, it can be assumed they used be much flatter. She was a professional stripper in 2010, so I don't think she'd be opposed to getting a little plastic surgery. She's showing off her huge butt after getting butt implants here.
Again, Blac Chyna loves to show off her famous rump.