A: Well, Plushies aren’t very good at knowing which cards are what, or quite how to play them, so sometimes they make mistakes, though they’ll gladly accept help in correcting it when it’s brought to their attention. “Oopsie! That should have gone down in front of you before! Here, take this card from the draw pile to replace it. Now, where were we…”

So, if they draw a Creeper… they’ll just accidentally have a Creeper in their hand for a while, and nobody will realize until it is revealed in the normal course of the game. At that point, just correct the error by putting the Creeper in front of them and drawing a card to their hand to replace it. (Of course, as usual, that play and draw don’t count against their total for the turn.) Then just continue with whatever action was happening, as though the Creeper had been played correctly before.

So if it’s the Plushie’s turn, they just proceed to take the Play they were taking when the Creeper was revealed, i.e. some other random card from their hand, and so forth.

If someone else was interacting with the Plushie, and it’s discovered, let’s say for example, by Trading Hands with the Plushie, any Creeper/s found to be in their hand would go in front of the Plushie, their hand would be replenished from the draw pile, and it would be that resulting hand which is Traded, as though it had been done correctly in the first place.