In Pokemon FireRed how do you get a grimer?

You can't get a Grimer in Pokémon FireRed. Grimer is a Pokémon that is only found in Pokémon LeafGreen.

Here's how you can get a Grimer in LeafGreen:

* Route 12 (Day Only): Grimer has a chance of appearing in the tall grass here, though it's not guaranteed.

* Route 21: Grimer is much more common on Route 21, especially in the tall grass along the western side.

* Pokémon Mansion: While you can find Grimer in the Pokémon Mansion, it is a rare encounter.

If you really want a Grimer in FireRed, you could trade with someone who has LeafGreen and ask for one!