A big heap of realistic Pokemon...

Whiscash (), a territorial catfish. Simple.
Cyndaquil, a distinctively colored hedgehog/echidna.
Mudkip, the larval stage of a very large salamander.
Totodile, a bipedal crocodilian similar to the ancestors of dinosaurs.
Chikorita, an interesting sauropod-like dinosaur with decorative feathers on its neck and head.
Natu, a bird of the arid tropics.
Chatot, a parrot. Nothing special here.
Magnemite, presented here as a rather interesting type of fly.
Skitty... It's just a cat.
Geodude (!) is presented here as a stone crab. It's easily disguised as a rock, and lives mostly on land (like a robber crab.)
Torchic, the immature fledglings of Blazikens.
Ampharos and Mareep (left out Flaafy... 'cause I don't like it.) are marsupials. When younger, they resemble long-tailed sheep, but lose the wool as they age and grow more kangaroo-like.
And Weepinbell/Victreebel... They're specialized amphibians that evolved parallel to pitcher plants... Victreebel scares me a little here.