Subterranean Homesick Alien
There's an elevator. There are two people outside the elevator. It should be obvious that one is an alien -- Antennae on their head, HELLO I AM AN ALIEN hat, t-shirt that says I ABDUCTED AND ANALLY PROBED YOUR MOM AND ALL I GOT WAS THIS PAINFUL RASH, be creative. The other is not an alien.
They get in the elevator.
Guy: What floor?
Alien: What? I'm not an alien.
Guy: Uhh. Ok. What floor?
Alien: Oh. The roof.
The guy pushes the button. (A real button would be scandalously decadent. Pantomime, you fools!)
Alien: Not that I have to go the roof to use my amazing alien technology to summon horrible spacely doom upon your puny Earth city! Ho ho ho! That I can do from anywhere. I mean can't do. Right. Not an alien. I just... want to... eat the birds. FEED! FEED the birds.
The guy nods & smiles politely, trying to be quiet and thereby encourage the alien to shut up.
Alien: Yes indeed. Entirely non-alien people in this here elevator.
The door opens (Ok, no props, right? Can you swing some elevator door sound effects? Some people going "Shoosh" "Shoosh" a la Star Trek?) and the guy is about to get out. The alien leaps out first, shoving him back in. The guy is unfluttered, once more.
Alien: Hah! Not so fast!
Guy: This isn't the roof. This is the fourth floor.
The alien looks around wildly. Ham it up so much it hurts.
Alien: (looking back at the guy at last) ... I bet you think I'm going to shout "PENIS" and run away like a crazy alien, don't you? Human fool!
Guy: I was expecting it, yes.
Alien: Well it ain't gonna happen.
The Guy leaves the elevator.
Elevator Door: Shoosh.
Guy: Now you must take the stairs to the roof! You fool! Who is the puny Earthling now! Ahahaha!
Alien: Curses! If only I could use stairs! Why is it that the alien mortal enemies of humanity always have some fatal flaw?!
Ok, technically I suppose that last line doesn't count as wholly original. Fair use, though, eh?