Chocolate + Peanut Butter + Cupcakes = Yes. At first I thought it was chocolate chip cookie dough on the very top-- which makes me think that could be tried, too. Chocolate batter, gob of peanut butter in the middle, cookie dough on top.
LOVE the frosting idea on these -- "Chocolate Peanut Butter Cupcakes - it's a basic chocolate cupcake but with a peanut butter buttercream frosting that is dipped in semi-sweet chocolate". Would mix with a different cake recipe, though.