There are not? I only know that back then, these event pokemon were distributed via downloads at Pokemon Day events. Didn't that involve downloading a wonder card via MG which then would trigger the event in the game that lets you obtain the pokemon? Similar to how you need a specific item in Emerald and onwards in order to reach the respective map locations where Mew, Darkrai and so on would be located.
I've considered simply adding the pokemon itself via .pk3 file too but if possible, I prefer the official way via triggering the event. It's how I got the event pokemon in the later versions too that involve the eon flute, old sea map and other event triggering items.