Calling a girl 'little sister'... Watch
It is weird, specially if the guy likes the girl :/ then they actually get mistaken for being real relatives by people that don't get their joke or whatever.... awkward
Whiskey Tango Foxtrot!?
I don't even call my younger sister that and she is around 5'1" tall thus qualifies by most authorities as being little.
Sounds like something Western people would call each other in a Manga film or something...