I have a Celebii... and all the other events exept Darkrai and Arceus (I got Shaymin because this one kid at the Manaphy event had an AR)
I got them from trades, exept my Manaphy which I drove over a mountain through 2 counties for an hour to get =3
Odd thing is, I STILL Need Groundon, all three dogs, Mewtwo, The birds, the Lati-twins, The Regiis (all four) Giratina and Azelf... ALL of wich I can get in the games I have...
The Regiis will be the hardest, seeing as Relincath only has a 2% encounter rate... >.<
My Pokedex:
(got)/(seen)/(out of a total of...)
365/402/493
I still have a ways to go...
I have all the Daimond exclusives on my Pearl, and I only traded for a couple of them)
Luckily I got Sapphire, which had the older Daimond exclusives... if I had worked for it a bit harder, I could've also gotten Murkrow (and Suicine) of FR... but oh well.
but no, it's impossible to "Catch 'Em All" without trading/another game.
for D/P, you'd need all the GBA Games (Main RPG) to get 'em all.
of course, that excludes the event legends... I got 'em all though, I just need to wait for Darkrai and Arceus...
Back in Emerald, if I did have 2 GBAs, I'd have all exept Zangoose... who now, I'd be able to get of my friend, so I'd have 'em all... in the Hoenn Pokedex.