The only way is to start the game with Treecko as your starter.
treecko
Ruby, Sapphire and Emerald.
Trade it from Ruby,Sapphire,Or Emerald.
Treecko, Tropius, Seedot, Oddish.
Treecko, Torchic and Mudkip.
Torchic, Mudkip, and Treecko
trade it over from emerald or ruby and Sapphire
The three starters: Mudkip, Torchic, and Treecko.
You must wait until treecko reaches level 50 or 51 and he learns it himself.
202 (Treecko - Deoxys)
Treecko or Mudkip. So do you liek mudkipz?
You can receive a Treecko from Professor Birch in Pokemon Ruby, Sapphire or Emerald. To get it in other games you must trade it as it cannot be found in the wild.