Crack open your briefcase or purse, and while peering inside ask: "Got enough air in there?"
Offer name tags to everyone getting on the elevator. Wear yours upside-down.
When arriving at your floor, grunt and strain to yank the doors open, then act embarrassed when they open by themselves.
Greet everyone getting on the elevator with a warm handshake and ask them to call you Admiral.
On the highest floor, hold the door open and demand that it stay open until you hear the penny you dropped down the shaft go "plink" at the bottom.
Stare, grinning, at another passenger for a while, and then announce: "I've got new socks on!"
Give religious tracts to each passenger.
Walk on with a cooler that says "human head" on the side.
Stare at another passenger for a while, then announce "You're one of THEM!" and move to the far corner of the elevator.
Draw a little square on the floor with chalk and announce to the other passengers that this is your "personal space."
Announce in a demonic voice: "I must find a more suitable host body."
As the elevator is going up, jump violently up and down, shouting "Down! I said down, dangit!"