We've got a smelly paper mill, a dirty creek full of turtles and sometimes an alligator, a bridge for smokers, stray cats, lots of bugs, and some messy art students. So I'd say:
Grimer, Muk, Trubbish, Garbordor, Koffing
Magikarp, Croconaw, Feraligatr, Squirtle, Wartortle
Pidgey, Starly
Meowth, Purrloin
Butterfree, Ledyba, Ledian, Heracross, Pinsir, Nincada, Venipede
Pachirisu
and of course Smeargle.
Grimer, Muk, Trubbish, Garbordor, Koffing
Magikarp, Croconaw, Feraligatr, Squirtle, Wartortle
Pidgey, Starly
Meowth, Purrloin
Butterfree, Ledyba, Ledian, Heracross, Pinsir, Nincada, Venipede
Pachirisu
and of course Smeargle.