How has categorization leached into our interpersonal lives? I plan birthdays, I give pep-talks, I care deeply, and — in more ways than one — I keep my friends sane and safe. Who am I? Ding! Ding! Ding!  I’m the quintessential ‘mum’ of the friend group.  Let's try another one … I am funny, witty, and usually self-effacing in my humour. Any guesses? Yep, you got it again … I’m the joker.  I could go on forever, but you get the point: friends have labels. The Cast List has been released, and...