Deranged as Possible!

I have an acquaintance who is a dynamo of creativity - an actor, writer, director. He's working on a web-based series. Today there is a shoot in the City. I have been cast in a very, very small role. Don't even have a line, although, I was told I could try to "improvise" something on the spot.

And what role have I snagged? Here's the description of the character I am to play, and well, in some ways, I have been totally typecast, and I wonder, how did he know?

"As deranged as possible, while somehow still fitting in society unnoticed."