Could there be a tag for a crossover obviously show the similarities in the characters' personalities? I know there's personality swap to create a bizarre comparison, but I don't see anything for when the personalities are similar, such as what I found below when browsing through Zero no Tsukaima and different crossover posts:
post #60931
post #97077 (expressionless waifs)
post #195017 (tsunderes, plus some Kugimiya Rie posts I saw)
post #670046 (tomboys)
post #726091
post #775386 (sadistic trolls)
post #127032 (yanderes)
post #198433
post #799396 (warrior women)
and probably other character types I didn't explore...
I know this would be a highly subjective tag and not used very much, but the above examples clearly demonstrate their similarities. I would also rule out the 'kind and caring' types because it is seen so much that it'd be impossible to tag them all.
**
On the other hand, I thought of there being a race connection tag where the crossover is because the two characters are from the same race, which I found especially noticeable with vampires due to Remilia Scarlet. I'd rule out humans and elves because they're so common, so other lesser races would count like vampires, monster characters and those with the same kemonomimi features (cat/dog/squirrel/etc).
Updated by jxh2154