It's the only way to go

lol

MissingNo ftw.

That, and pc glitches. You can get every legendary thru glitching up to gen 3 I believe. Of course, some require trade from older games to complete Dex, but the hardest by far is Celebi. The amount of steps and the rareness of getting it right...I fucked up, but it ended up in my favor, and I got a Celebi with PokeRus. That was cool. Had no idea what it was and had to look it up.