He is kind of swimming in the water behind the waterfall Shock him Magikarp comes out of water. This place is also in a shady area.
Shroomish is in a crate in the meadow zone. It's close to where you find Magikarp.
Not there
Play park
set a record
He is in the beach zone
Magikarp can be found behind the waterfall. Face the water and use Thunderbolt, it will then pop out.
bayleaf is not on pokepark wii only chikorita is
Talk to everyone
go to the meadow zone then the lake and use thunderbolt on it it'll come and ask u if u want to play chase
In the Train Depot in the second game
Around the Drilling Machine where Hitmontop is
Can't find either maybe not a Pokemon in this game