one of them being that you can wrongwarp to a fake sinnoh, but in the RAMsection of mapdata.
This is very useful since that means I can go to the coordinate of shaymin's area and then manipulate ram
there to change it to a jubilife. Then save resetting there allows you to get to shaymin.
Sadly from what I see darkrai won't be obtainable in the same way, since the coordinates put you very high in mapdata,
so high in fact that entering a mystery zone will even overwrite those bytes.
Edit; video showing this in action: https://www.youtube.com/watch?v=0wPS4wpDSTI&t=1s
have entered bottom floor of pokémon center
have entered contest hall
enough balls to capture shaymin
Anyway, this is the route;
If you ever done a wrongwarp before, utilise the mapscript-based route to wrongwarp instead.
If you've done it before doing the steps shown will crash your game.
If you dont have wrongwarp setup; following steps
Full speed South until wall (480 S, don't stop)
then you graphic reload, and go up to meet shaymin
I will attempt some more at a darkrai route but don't get your hopes up for that one.