First, I measured the existing sign, which got me some strange looks in the elevator. Then, I used Inkscape to draw the existing sign, as well as the changes I wanted to make:
Our lab has a big printer for printing posters, and things like that, so I printed the "very temporary" addition out on it and trimmed out the center:
With a few pieces of masking tape on the back, I was ready to go! I rode up to the 13th floor, held the door open with my backpack, and attached the sign:
Anyway, I rode the elevator up and down for around 15-20 minutes to see people's reactions. I don't have the hidden camera/microphone supplies of the Improv Everywhere guys, so you'll have to take my word for the reactions. Most people either didn't notice or didn't react. Some people thought it was funny (one or two camera phone pictures were taken) and some people got very confused. I needed to leave the elevator eventually because some guy noticed I kept riding the thing up and down (also, I was getting a bit motion sick).
I printed a second sign that got the width right, but I still need to adjust the color and height.
I don't know how long these ultimately stayed up for, because I eventually got a bit dizzy again (and I also had work I needed to do...).
The really strange thing, though, is that I think someone else might have been pranking the system at the same time! I noticed that some floor signs outside the elevator had been covered:
I'm thinking this might have had a better effect if I covered the existing sign, but that might seriously confuse innocent people and the sign would probably have a mush shorter half life. Maybe I'll give it a shot anyway, though (April 1st isn't that far away...). I'd love to hit all 3 elevators at once (maybe I'll rope my labmates into helping out), so, if anyone has any ideas for other symbols to mix up in the labels, let's hear 'em (someone already suggested The Artist Formerly Known As Prince's strange symbol). Also, if anyone has ideas for a way to cheaply and inconspicuously record people's reactions, let me know, too.