I’ve found this impressive list of IPB easter egg on thevistaforums , but you would have to register to view.

This includes the little jokes the developers write in the comments and what they use to name the functions in their php classes.

If you want to really have a laugh just read it,

here is one easter egg that everyone knows about:

http://icelabz.net/forum/index.php?act=Stats&CODE=who&s=ugly_old_matt