All you have to do is have another Pokemon GBA game sitting in your DS at the time, and different Pokemon than normal will show up in an area.
Growlithe can be found with FireRed on Routes 201 and 202.
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In Pokemon Platinum, you can't catch an Arcanine, but you can catch a Growlithe and evolve it into an Arcanine. To catch a Growlithe, you have you use dual-slot mode with FireRed in the second slot and then you should have an 8% chance of catching a Growlithe on Routes 201 and 202 in Platinum.
There is a very special way in which you can get Growlithe in Pokémon Platinum version. You can find Growlithe on both Routes 201 and 202. There is a catch though, you need Pokémon FireRed Version inserted in the GBA game slot.
you have to trade it from another game or get an action replay
The Pal Park.
There aren't any Growlithe in Pokemon Ruby, but you can trade for them from Pokemon Fire Red or Pokemon XD.