They do look similar, and some people genuinely can't help having trouble with faces.
But I hope pointing out pointy bangs for Diane can help.
Lots of triangles.
As a personal favor, please don't joke to me about not being able to tell them apart? If sincere, fair enough, but I want to actually know if people are having trouble and why. I see this as a problem I am trying to solve, and I require accurate data for SCIENCE!!!!!!!!!