With apologies to René Magritte. 

Did you know you could stop the treachery that is Rickrolling hyperlinks with an iRule? Just search your outbound HTML for the appropriate YouTube URLs (you may need a data group to store them all) and strip them out, or search your inbound posts for the URLs and refuse to post them.

Of course you could also write an iRule that automatically changes every submitted URL to be a rickroll, but man, that's evil! Maybe you just want to do it for a specific user. You can do that with iRules if your site uses cookies to identify users by id or name. Just check the cookie and if you find the right user, fire off the appropriate iRule code to replace the URLs before it's posted.

It would still be evil. But it would be funny evil, if you know what I mean.