I deided to check all of the Pokemon on my "Pokebank" Box and check which ones counted as were legit and which ones weren't. I detected THREE Non-Legit Celebi and 1 non-legit Shaymin. Turns out I will only be having the Pokebank Celebi after all. I altleast have the Flower Garden Shaymin in Platinum to spare tough. I also noticed that I have the Hall Of Origin Arceus, and I wonder if the Poke Transferrer will think it's legit or not. If not, then who cares, I still have an Event Arceus in Soul Silver.
After that, My list is Kyogre, Rayquaza, Thundurus, Tornadus, Landorus, Victini, Meloetta, Genesect, Keldeo, Zekrom, Oshawott, Tepig, Mudkip, and after that, I'll just need to evolve some Pokemon and my National Dex will be complete as well.
I could Pokegen the Event ones and Just move my Arse and get the genies (which isn't hard) but Serebii Net doesn't give you the SID of the Event Pokemon, so It's not safe at all. I didn't find the cheats for the events either. Dammit.
I just read somewhere that it uses Pokemon Battle Revolution's Legit Pokemon Checker. OKAY EVERYONE, WE DON'T HAVE ANYTHING TO WORRY ABOUT ANYMORE, THE ONLY THING IT'S GONNA BLOCK ARE POKEMON WITH MORE THAN 510 EVS, AND ONLY SOMETIMES.
Hell, my experience with PBR's Checker: It once let my neighbour transfer a Route 201 caught Deoxys to it. So it probably won't stop anything unless it's really blatantly hacked, like 99IVs on all stats, 999EVs on each stat and no PID. (Maybe that is what stopped Suikama's Mew, maybe it had no PID)