you simply can't. I'm sorry. but there's just no legitimate way. you can use a game shark if you are of 'lesser morals', though.
You can get Chikorita in Pokemon Gold, Silver, Crystal, and Emerald.
The three starters in Pokemon gold version are Chikorita, the grass type, Totodile, the water type, and cyndaquil.
Either have it as a starter in Pokemon Gold, Silver, Crystal, Soul Silver, or Heart Gold. In Pokemon LeafGreen and FireRed you'll need to trade a Pokemon for it. Also in Pokemon Sapphire, Ruby, and Emerald. In Pokemon Diamond, Pearl, and Platinum you have to trade a Pokemon for it. Hope this helps!
chikorita
Pokemon #151 Mew. Pokemon #152 Chikorita.
Chikorita is a starter pokémon in Silver, Gold, Crystal, Heart Gold and Soul Silver. If the games are compatible you can trade a Chikorita from one of those games to your own. I don't believe you can get a Chikorita in the wild.
You can get Chikorita in Pokemon Gold, Silver, Crystal, and Emerald.
Chikorita is a starter Pokemon in soul silver and heart gold you can't find it in the wild, but if you just want to battle it some trainer may have it.
You cannot catch wild Chikoritas in any official Pokemon game.
Chikorita, Totodile, and Cyndaquil
Chikorita, Totodile, and Cyndaquil.
There are actually a few games with chikorita as a starter pokemon: Pokemon Silver (GBC) Pokemon Gold (GBC) Pokemon Crystal (GBC) Pokemon Soul Silver (Nintendo DS) Pokemon Heart Gold (Nintendo DS) You can also get chikorita as a present for completing the Hoenn Dex in: Pokemon Ruby (GBA) Pokemon Sapphire (GBA) Pokemon Emerald (GBA)
Unfortunately, you can't catch a Chikorita in the wild. You'll only be able to find it if you choose it as your Starter Pokemon or you chose a Totodile as your Starter (in which your rival will choose the Chikorita). Or you can trade another Pokemon for it in the GTS.
In Pokemon Gold/Silver/Crystal/Heart Gold/ Soul Silver you can have it as a starter but otherwise the only way to get it is from trading.
Chikorita has around 17.5% chance to be a female, so keep soft resetting til you get one.
Same thing as Pokemon Silver and Gold: Totodile, Chikorita, and Cyndaquil.
Cyndaquil / Fire , Totodile / Water, Chikorita / Grass