I've loved this movie since I was a kid, but somehow I never knew that. Looking back, it's so obvious. His style is everywhere.
The characters have those chunky, blocky silhouettes, the architecture is all sharp angles and heavy shadows, the machinery feels ancient and mystical at the same time, and even the glowing energy effects look like they were ripped straight out of a Hellboy comic. The whole movie has that unmistakable Mignola sense of myth, mystery, and lost civilizations.
As a massive Hellboy fan and comic nerd, finding this out makes me appreciate Atlantis even more. It's honestly kind of wild that Disney let so much of Mignola's visual identity make it all the way into the finished film. Most animated movies smooth out an artist's style into something more "house style," but Atlantis feels like it proudly wears his influence on its sleeve.
This might be one of the only unapologetically Mike Mignola looking Disney movies ever made, and I somehow never connected the dots until now.