It's both!
The actual pin is Minnie in a bathing suit, with a regular tie-tac backing. Then there is a gown and a crown which stick on her magnetically, and are removable.
(Personally, I know I'd lose all the little magnetic parts, so I'm passing on this pin. By the time I was done playing with them, none of my Barbie had two matching shoes and I had very few hotels to put on Monoploy. I lose little parts like this, I don't want to have to keep track of pin parts!)