What goes up and down the stairs without moving?

Nothing.

a dead body carried por two clumbsy murders

the rug and/or the banister(handrail)

The stairs it's self.

the railings, it's true, also true @seffro :D XD

The carpet

The actual steps..?
The hand rails?
The carpet, if there is one..
My ninja buddy?
...Eh, I know what goes DOWN the steps without moving. That'd be me.. I just lay there and slide down the steps on my back. I'm sure my parents are proud. :')

The floor.

Chuck Norris?

A.......A dick?