Pokémon Name: Rattata
Type: Normal
Classification: Mouse Pokemon
Pokédex Number: 019
Ability: Run Away and Guts
Dream World ability: Hustle – Boosts user's physical attack power by 50%, but lowers physical attack accuracy by 20%
Useful Attacks: Hyper Fang
Location Found:
D/P/P: Routes 225 and 226
HG/SS: All over the place
B/W: Breed Raticate
Another simple, two-step Pokemon good for stomping through early-level trials. But, seeing as you don't see Rattata until way late in the Diamond and Pearl region, its usefulness is suspect. Grab one for completion's sake, then grab another to evolve into Raticate.
Evolution: To Raticate at 20