Bellsprout

Evolution

Bellsprout, the Flycatcher Pokémon. Bellsprout is a Grass/ Poison type Pokémon, and it evolves into Weepinbell at level 21. Weepinbell then evolves into Victreebel with a Leaf Stone.

Red, Blue and Yellow

Bellsprout was introduced in Red and Blue Version. It’s #69 in the Kanto and National Pokédex.
Bellsprout can be caught on Route 5, 6, 7, 12, 13, 14, 15, 24 and 25 in Pokémon Blue, and on Route 12, 13, 14, 15, 24, and 25 and in Pokémon Yellow. Bellsprout cannot be caught in Pokémon Red Version. More Version Exclusive Pokémon

Gold, Silver and Crystal

Bellsprout in Gold and Silver got some new traits. There is now breeding, so Bellsprout can either be male or female, and it’s in the Plant egg group. Bellsprout can be bred or caught Shiny as well.
Bellsprout can be caught in Gold, Silver and Crystal on Routes 5, 6, 24, 25, 31, 32, and 36.

Ruby, Sapphire and Emerald

Bellsprout cannot be caught in Ruby, Sapphire, or Emerald; you have to trade it from FireRed or LeafGreen. In Ruby and Sapphire, Pokémon got Abilities, and Bellsprout’s is Chlorophyll. Chlorophyll doubles the Pokémon's speed when it's sunny in battle.

FireRed and LeafGreen

Bellsprout can be caught on Route 5, 6, 7, 12, 13, 14, 15, 24, 25, Berry Forest, Bond Bridge, Cape Brink and Water Path in LeafGreen. You can then breed Bellsprout and trade them over to Ruby, Sapphire, Emerald and FireRed if you want.

Diamond, Pearl and Platinum

Bellsprout can be caught in Diamond and Pearl on Route 229 and 230. Bellsprout can be caught in Platinum on Routes 224 and 230. If you migrate a Bellsprout from any of the Advance games, you’ll find Bellsprout in the Forest area of the Pal Park.

HeartGold and SoulSilver

Bellsprout can be caught on Route 31, 32, and 44 in HeartGold and SoulSilver.
While not exactly in HeartGold and SoulSilver, you can catch Bellsprout in your PokéWalker if you're strolling in Noisy Forest.