This is a set of Adventure Time character nesting dolls available from ThinkGeek ($25). Pretty cute, right? You know, I got a set of traditional Russian nesting dolls for Christmas when I was a kid. There were so many of them! I wound up accidentally swallowing the tiniest one though. "What was it doing in your mouth in the first place?" My mom asked the exact same thing!
Thanks to Jeff M, who mentioned having a set of EROTIC nesting dolls. Ooh la la!