Early route Pokémon are a set of Pokémon that are found in the first few routes of every game.
In each generation of Pokémon games, there is always an early route Pokémon that are available in each of the game's first few routes, usually they are Normal-type, Flying-type, and Bug-type Pokémon. They usually evolve around level 5-25, and their evolution can also be found in the latter routes.
Rattata (コラッタ Koratta) is a small, but unspecified rodent. It is a Normal-type Pokémon. Its most notable feature is its large teeth. Like most rodents, their teeth grow continuously throughout its life, and must be constantly worn down by gnawing. It will bite anything when it attacks, though it will live peacefully side by side with Pidgey. It evolves into Raticate starting at level 20.
Pidgey (ポッポ Poppo) is a Normal/Flying-type Pokémon. At Level 18, Pidgey will evolve into a Pidgeotto, which then evovles into a Pidgeot at level 36. It is one of the first Pokémon that you find in Pokémon FireRed/LeafGreen.
Spearow (オニスズメ Onisuzume) is a small Normal/Flying type bird Pokémon with short wings and a stubby beak. It is noted for being frail. It eats insects in grassy areas by flushing them out with its wings, and plucking at them with its beak. It Evolves Into Fearow at level 20.
Taillow (スバメ Subame) is a Normal/Flying-Type Pokémon. It can evolve into Swellow at level 22, and has no pre-evolutionary stage. Its special ability is Guts. It has a gutsy spirit that makes it bravely take on tough foes. It also flies in search of warm climates. It will fly around, looking for tasty Wurmples to eat.
Wingull (キャモメ Camome) is a Water/Flying-Type Pokémon. It has no pre-evolutionary state, and can evolve into Pelipper at level 25. Its special ability is Keen Eye. It makes its nest on steep sea cliffs. Riding updrafts, it soars to great heights.
Pidove (マメパト Mamepato) is a Normal/Flying type Pokémon introduced in Generation V. It will appear in Pokémon Black and White. Its class is a Baby Pigeon Pokémon and has the abilities Super Luck and a new one called Big Pecks which seems to prevent the defense stat from falling. It is also revealed that it learns Gust. Pidove evolves into Tranquill at level 21 and then into Unfezant at level 32.
Wurmple (ケムッソ Kemusso) is a Bug-type Pokémon introduced in Generation III. Wurmple's only known moves are Tackle and String Shot. At level 5 it learns Poison Sting, seeing it has two stingers on its rear. When Wurmple reaches Level 7 it will evolve into either Silcoon or Cascoon, depending on its personality value (example: a Wurmple with a bashful nature will evolve into Cascoon.
Kricketot (コロボーシ Koroboshi) is a Bug-type Pokémon that is found in the Sinnoh region. It evolves in Kricketune at level 10. When you catch a Kricketot it can have a Metronome. Kricketots special ability is Shed Skin.
Sewaddle (Japanese:クルミル Kurumiru) is a Bug/Grass-type Pokémon and it's classification is the Sewing Pokémon. It is a Generation V Pokémon that will appear in Pokemon Black and White. It has the abilities Swarm and Chlorophyll. It knows a new move that can hit two opponents called Struggle Bug. It evolves at level 20.
Venipede is a Bug/Poison-type Pokémon. It is based on a Centipede. It evolves at level 22 into Whirlipede, which evolves into Scolipede at LV 30.