Me as a Slurpuff.

A Slurpuff is two feet and seven inches tall (that's the same height as Rok, what do you know!) yet weighs a measly 11 pounds. I imagine its body composition is like a spongy cake or a mousse, deceptively light and fluffy for how much it jiggles.

Edited 11/26/2019: I don't normally ever go back and make changes to my work after considering it done, but I wanted to add a tail. My thinking is that when you eat enough of a pokémon candy, you transform into the base form. Eat way too many and you'll evolve at the same time, and sometimes features from the pre-evolved form remain. Hence, Swirlix tail.