Pokemon Mystery Dungeon: Explorers of Time

I believe that it is impossible to find a working password which will allow Mewtwo or Celebi on the versions they don't normally appear. The only known way to break this limitation is by getting the missions from Wi-Fi, and the event for USA is already long since over. These particular Wonder Mail don't even show passwords, even though they are treated like any other mission.

These missions can be transferred from DS to DS, so if anyone in your area happened to get these missions and have not done them yet, this might be your only non-cheat way of getting one of these legends. I hear "Europe hasn't gotten that WM yet", so if you happen to live there, then all you have to do is wait for that mission to eventually appear on Wi-Fi.

Although I have a very complete and thorough knowledge of the Wonder Mail system, even as far as creating working passwords from scratch by hand, I still could not create a Wonder Mail that allows these legends to appear.

My attempts are in an archived topic, here:
http://www.gamefaqs.com/boards/genmessage.php?board=938930&topic=45046987

... And those attempts ended in failure. I say again, I believe it is impossible to find a working password that allows Celebi in Darkness or Mewtwo in Time. I hope my belief is proven wrong, though...