I work in midtown Manhattan.
Last week, I put this up on my office window.
A few days went by with no response, so yesterday at the suggestion of a coworker I changed it to "JELLO."
A few hours later, look who appeared on the opposite window.
I thought that was pretty nifty creative genius.
They replied again, still stuck on Jell-o.
Well, ok.
Update: It turned out that wasn't the end of the story. So the story continues in this post. Also, there is a great short film inspired by the same idea, directed by Patrick Hughes.