u'know how in gakuen hetalia, romania and bulgaria didn't like each other at first? but then they became friends? u'know how before they became friends, they fought and later, bulgaria would throw balls of crumpled paper at romania?
so imagine:
bulgaria *throws a paper ball at romania and hits him in the head*: HEADSHOT! *laughs*
romania *grabs his book and slams it into bulgaria's face*: FACEBOOK!