Cryptic

We came up with a good idea for our Halloween costumes - we are going as a group. A bunch of my friends, that is.

I am going to give you a puzzle. Guess what our costumes are. I will give you two hints:

1. wheelchair
2. superheroes

Those are two very bold hints. Someone has to get it.

Now tell me, how bad is it to hide a hospital wheelchair until Halloween?
The wheelchair was abandoned in my building by someone else, several weeks ago. I did not steal it from the hospital.
I didn't steal it from some old granny who needed it (Garrett suggested I might have done this. I did not!)

AND! I plan to return it to the hospital when I am done. That's more than was happening with it before I acquired it. That's not bad, is it?

Let me know. I would really like to know.
Oh yea, let me know what your guesses are about our costume idea.