Does anyone else try to spot all the tags in the picture? If so, can someone let me know which one of these kids has three eyes?

Nina's wolf costume in panel 4 has a visible blue eye, just above the tongue. That's presumably what's meant.

(I'm not sure that sort of thing is what the tag is meant for, but it's accurate by the wiki definition of third eye.)

Oh my god, you're right! Wow that thing is hidden! Much respect Sincere!