Diamond and Pearl: Never-ending cheat on how to obtain Celebi

[Aruseus Rider]

You must go to the region of Ouen (Dragonfly cave,anyone?)
Then take a Monarking (Pokemon from the story) and beat the
crap outta it and and it will teleport you to Barney Land.
Then....

 

[Vuallum]

You will find out by the carnage, rubble, and fire surrounding you that Barney's gone insane. Prof.Elm calls you, and tells you that he will be able to find your exact location and send a Kadabra your way to teleport you out of there.
This won't happen for 3 hours, during the 3 hours you must defend yourself against Barney and not let your entire party faint, if you do, you will get the classic sonic "GAME OVER".

If you pass the 3 hour Barney defense task...

 

[Rivvon]

...you will be visited by the Four Fairy Peas of Christmas, and using their strawberry cheese powers, they shall...

 

[Jamie006]

...transport you to the truck near the S.S. Anne, which...

 

[Blaziken_Boy]

Will start to roll down to you. Press Z or R twice to do a barrel roll into der water and find Jaws. Use the Park Ball you should've gotten for nothing on him and catch him, then use him to fight the Red Gyrados. He'll a'splode and teleport you to a look-alike of Lake Verity when it 'sploded. Eat the right Magikarp, if you try eating the wrong one it'll become the rattata and eat you. Then you...

 

[Cobja619]

Take a trip into Viridian Forest. Talk to the first guy you see and he will give a gun. Suddenly your game will self-destruct. Go down to Cash-Convertors to buy a new game. Oddly it will be at the same stage, so walk into some grass. The Celibi will appear. Send out a Lv. 100 Magikarp with the moves FISSURE, SHEER COLD, HORN DRILL (Somehow...) and FRENZY PLANT then without hessitation, search your key items and select your Gun. Shoot Celibi in the face and it will flee. The only way to get it back is to.....