I tried using a band of misfits as a ratcatcher. It put it down to the mat, but there wasn't any option to retrieve it and actually use it to trash a card, it was just permanently down on the mat.
Not a bug: as soon as Band of Misfits is moved to the Tavern mat, it's no longer in play so reverts to being Band of Misfits rather than Ratcatcher and hence loses the ability to be called. Moral: don't use Band of Misfits or Overlord as a Reserve card.