Shapeshifter promo card for Adventure Time Munchkin?

[Munchkin JK]

Does anyone know what the story is with the Shapeshifter promo card for Adventure Time Munchkin? It's listed on BGG.com along with the Grass Sword promo card and the flavor text specifically mentions the dungeon deck which just came out this week with the new expansion.

I asked my FLGS about it yesterday when I picked up my copy but they didn't know anything about it and I'm not seeing it pop up on ebay or anywhere. What's the what??

Here's the link on BGG