Gusy want to know , if anyone in their software career planted easter egg in the code and blew up in the customer site.

PHP has an easter egg feature that is a bit far-reaching, not sure if you can call it a security weakness (as expose_php needs to be on for it to show, but if it's on then PHP gets also exposed via the http header) but I guess it could allow people to scare a manager asking them what odd images are on their server...
http://www.0php.com/php_easter_egg.php

All I get when I tried just now is the blurry images, no more dog...

By the way what's the background of your question?

i was hearing from my friend while during acceptance testing , a easter egg in the form on NoShitException placed at not reachable in remotest possibility, occured in the client site. any moments like these from forum members.