I believe you have to trade it from Pokemon Emerald.
you have to catch 151 Pokemon and then go to professor oak . He will ask you to take one Pokemon from the three Pokemon , the Pokemon are chikorita , cyndaquil and totdile.
You can but only from trading with Pokemon emerald or Pokemon colosseum.
A ditto and a feraligatr
It evolves at level 16.
Well if you have a Nintendo DS and you have firered or leafgreen insert it in the bottem then go near the beach in pastoria city go near the grass use a max repel then use Pokemon seeker then keep doing it on and on you can only do this is you have the 8 bages Im testing it now
Feraligatr (Johto starter) evolve crocnaw which evolves from totodile (the only way to get a totdile is to complete the pokedex in emerald and talk to prof. birch)
waterfall pond 10F
after you finish your pokedex prof.oak lets you choose between a totdile,cydaquil,or a chickorita
Evolution wise, you will get a Croconaw once it reaches level 18 and a Feraligatr once it reaches level 30.
Johto Starters: Chickorita,Cyndiquil,Totdile New Bark Town, Elm's Lab Kanto Starters:Bulbasaur,Charmander,Squirtle Pallet Town, Oak's Lab Hoenn Starters:Treeko,Torchic,Mudkip Saffron City, Silph Co. Green Stone: Treeko Red Stone: Torchic Blue Stone: Mudkip