Probably the most elaborate prank that I ever pulled was back during my college days with my best friend and then housemate. What we did was write letters and postcards from abroad to a third friend that lived in another town - and made him think that we totally moved out of the country.
Here's how the set-up went:
I wrote to a cousin of mine in Manila and asked her to send me about 4 blank post cards from the Philippines.
Between my friend and I, we each composed 2 bogus letters apiece in which we made up stuff in which we both went to the Philippines on vacation and described our adventures. With the 4 postcards that I got from my cousin, we each wrote some typical BS about how we were enjoying ourselves, yada yada.
The correspondence that we wrote was sequential by design: the first letters and postcards first told of how we went to the Philippines on vacation ... but as the later correspondence was sent, we wrote to our friend "back in the States" that we both decided to give up living in the US and take on work in the Philippines.
Once we had completed all the postcards and letters, I packaged the whole lot off to my cousin in the Philippines. Once she received our package, she would find that we had everything already addressed and ready to be mailed back to the US. I sent her some money for postage and she followed up on our elaborate, long distance prank. Her instructions were to use the money I gave to pay for
Philippine postage and then mail off the specific letters and postcards in weekly intervals to our friend back in the States.
The friend that received all our letters and postcards totally fell for the whole joke. He totally believed it because he knew our handwriting, the postcards were for real, and the international postmarks on all of the correspondence were truly authentic. He really thought that we left the US on vacation and then decided to just live in the Philippines for good. Little did he know that me and my friend not only were 30 minutes away from him but that we were both living together as housemates. The initial month or so that we perpetrated this gag was a little hairy because we actually had to have other mutual friends and family corroborate our practical joke whenever our friend would call on them for verification. But after a while, he ended up becoming convinced and stopped questioning it.
Believe it or not, we perpetrated this ruse for nearly 6 months until we finally let the cat out of the bag.
Since then, I don't think I've ever played a practical joke that was this elaborate or long-running.
Well, not until I created this HERMIT persona.