You can’t get the couch into the elevator, typically. Trust me, I tried.

Couch depending. I will persist in trying every time this comes up.

You can take a mattress up an elevator though (1). Some couches might fit in some elevators.

1: source: me...

Well if it's one of those hospital elevators that can take a bed with a patient, you probably could. Or if it's a small 2 seater sofa. The question isn't as dumb as it sounds at first, and a human would definitely ask a follow up question.