well it depends either you or your rival if you chose mudkip its your rival if you chose it, there you go but i'm not sure if any other trainer has it.
Ruby, Sapphire and Emerald.
Treecko, Tropius, Seedot, Oddish.
If you are talking about the starters..then,U are able to pick from Torchic,Treecko,Mudkip.
In Pokemon Sapphire, there is only one trainer in the game that has a Ludicolo. To find her go to Victory Road and search around everywhere and you will find a pokmeon trainer that has a Nosepass LV 42, Ludicolo LV42 and Medicham LV42.
For Ruby, Mudkip. For Sapphire, Treecko. For emerald I do not know
treecko
In Ruby, Sapphire, and Emerald, there is only one possible way for another trainer to have a Mudkip. In the beginning of the game, you have the option to choose one starter Pokemon. If you choose Torchic, your rival will choose Mudkip. Your rival will always take the Pokemon that is elementally superior to yours. You choose Treecko - They choose Torchic You choose Mudkip - They choose Treecko You choose Torchic - They choose Mudkip
The only way is to start the game with Treecko as your starter.
Ruby, Sapphire and Emerald.
Trade it from Ruby,Sapphire,Or Emerald.
Treecko, Torchic and Mudkip.
Treecko, Tropius, Seedot, Oddish.
Torchic, Mudkip, and Treecko
The three starters: Mudkip, Torchic, and Treecko.
trade it over from emerald or ruby and Sapphire
202 (Treecko - Deoxys)
Treecko or Mudkip. So do you liek mudkipz?