Fun mimic encounter, Advice needed.

Hey Reddit,

Hope you're all rolling your natural 20's

I'm planning an encounter and I was wondering if we could make something memorable :) so I'm turning to Reddit. This is the premises of the encounter I have.

The party is currently in an asylum dressed as clerics (though none of them are clerics) they are there to rescue someone, but in the meantime they are going to stumble upon an inmate who is convinced they are a mimic. They are going to have a doll as the inmates wife who is an actual baddy, while the guy is a mimic. During the encounter I'm going to have Mr. mimic run behind objects and pretend to transform (he's basically going to hold onto the object and think he's that object)

My question is what fun objects can Mr. mimic have in his Asylum Cell (The inmates are well looked after) that he can hide behind and polymorph into as the party fight a demonically possessed doll?

So far I have:

A ladder, A stone, A classic treasure chest He's going to stand by the bars and convince others that he's part of the cell.

Any other ideas!