Wario is using true Japanese cartoon artwork, so the look is totally authentic. As for the origins of this thread though and the comparison to cel-shading, how many animes have you seen where the character is centre-screen, side-on profile for the whole episode?! Comparing to the likes of Naruto, with their special effects, 3D viewpoints rather than static side-on view, and other dramatic stylizations, the Cel shaded engines are definitely closer aproximations of hand-drawn stop-motion from the studios of Japan.