You can only catch the you encounter in each area.
You surf to the Seafoam Islands expecting Articuno. You climb down. At the bottom, instead of a frozen bird, a sits on the pedestal. You didn't expect a Johto legendary in Kanto. That is the "Better" randomizer working—it blends generations seamlessly. pokemon+fire+red+leaf+green+randomizer+rom+better
: A classic "enhancement" hack that increases difficulty and variety without adding the extreme complexity of Radical Red Pokemon Crossroads You can only catch the you encounter in each area