In diamond and pearl, there seems to be a cloning glitch via GTS. Here are the steps from what I've heard from on the serebii.net forums.
1: Log onto wi-fi via GTS 2: Offer pokemon on the GTS 3: While it gives the waiting message, look at the bottom right at the clock on the message. When it turns 7 and a half times, turn off the DS. 4: Go back to the GTS. There should be a clone on the GTS, waiting to be traded and one where it was originally.
I, myself, haven't done this, but people on the forums claim that it works.
Oh wow, I just found this site and I have something that I've been wanting to share about generation 2 cloning for a while now. Okay here's my story (I have a witness to it but frankly, believe it or not, I dont really care): One day I was cloning my suicune and wanted to see if I could clone more than one pokemon by just depositing another with it. Sure enough it worked. The other pokemon was a tyrogue. So here I was, with 2 tyrogues and 2 suicunes. I decided to go train one of them to evolve them into a Hitmontop (which I had really wanted). So I started leveling it up, and this is where the strange stuff begins. It began learning the moveset of my suicune! I don't know why but I specifically remember it only learning suicune moves. It was on pokemon crystal that I tried this. Since then my crystal version (along with my gold and 2 silvers) has stopped working for no apparent reason. I don't remember if I did some extra step or something as it was done 3 or so years back... Any info on what happened to me would be much appreciated. -PyroSprite-