But it would be worth it to have unlimited Celebies. I wonder if a shiny Beast/Dog/Cat exists somewhere....Hmm
Yes.
No? The shiny legendary beasts for HG/SS were given away via Wi-Fi. o.o
Apparently not. There actually is a cartridge of it. I thought I mentioned that earlier in this thread... the seller I got the Celebi one from actually did have the shiny dogs at one point, as he had photos of it in his gallery, but he said it was already sold.

I wanted that one too! 3 Pokémon, and shiny ones at that, are totally more valuable than just one! LOL
Wasn't there also a Regigigas one?
There are plenty of them. The question is, how many have been leaked and end up on eBay? I honestly don't know - I have a ROM of the Deoxys DP event from 2008, but have never seen the physical cartridge. Basically ANY GameStop or Toys R Us event was on a DS game card at some point. It's how the stores did it. But some stores are actually good about returning their stock to Nintendo... technically NONE of these are supposed to be on the market, I just happened to get lucky

--EDIT--
Whoops, totally didn't see the second page.
There was a Regigigas event, where, on Platinum, would allow you to a set of the three golems (which in turn can lead you to another Regigigas, I believe).
That is correct. I've got it. Not sure which store it's from but it's definitely a store event like the rest of them were. No, I don't have the Regigigas event card though.