Okay, usually pranks like this are really lame. People who call in or write in to a show and just scream something stupid, or say some inside joke that only a few friends will get are just dumb. You’re not impressing anybody.
On the other hand, sometimes there are clever pranks, which are done well enough that the person who is pranked just has no clue. Case in point #1:
Even better would be if you could subtly Rick Roll someone while they are talking about being pranked:
Links via Urban Prankster.