What t-shirt graphics or text can attract attention of an amazing developer at a conference?

I want to find and hook a super-passionate iOS / Android developer with a cool message on my t-shirt. Maybe a code snippet or a clever coding joke + a call to action. Maybe a call to action written as a code or a challenge to find an error in a code. Anything that could help to start a conversation :)

Bonus points if this graphics or text attracts a professional, not just somebody who knows what a programming language is called.

Many thanks!