cephalopod eyes
Eyes unique to octopus and squid.
Look for pupils that vaguely resemble a figure 8.
- Obvious examples: Danbooru post #6656274, Danbooru post #4069806
- Subtle examples (nearly identical to rectangular horizontal pupils): Danbooru post #6223494, Danbooru post #1660157
Use horizontal pupils or slit pupils where applicable.