On Bulbapeidia they have somehting on the Japanese D/P Glitch where you get stuck or something but this quote from Pokecommunity could be it,
Darkrai Island ( Right translation? ) :
1. Use the E4 Glitch (Explained at the top)
2. Land back on solid ground (black abyss) when you go south.
3. RESET your step counter.
4. Go 200 steps EAST from the door you just left.
5. Go 254 steps SOUTH. (If you need help, then the total is 454.)
6. Then go 54 steps WEST (508 steps in total)
7. Then, use the Underground Kit (I don't really know what this is, because I don't own the game…)
8. You should appear Underground, so resurface (Again, I don't really know how to do this…)
9. You will apparently be in a glitchified ground.
10. Check your MAP key item to have it stop glitching.
11. Now, you can catch Darkrai. Remember, that you need FLY to get out. So far that I know of. Please correct me if I am wrong.
There were youtube vids but
Well, the YouTube videos are gone now, thanks to Pokemon USA. Yay for them, and now we can't see them again.
and the Cloning trick is Legit BTW.It never works for me because I suck at it xD
Actually the Shemi [Shaymin or whatever] glitch is legit but only for Japan I believe cause yanno NOA took out ..the glitches :P
Hey I have an imported version of Pearl, and I tried it! I know, risky huh? Anyway if you follow the directions exactly as followed it really works! I now have a Sheimi on my team!!!! Also it was really easy to catch I just used a dark ball on it after i got it into the yellow, it wasn't asleep or anything.
and Nintendo has posted solutions to both bugs. according to IGN.