Comes from the idea that
Shakespeare wrote plays whenever he felt like he needed to complain about some aspect of his life.
If someone is complaining, whinging, sulking, bitching or moaning about
something, no matter how
pathetic or meaningful it is, you can tell them to write a play about it to shut them up.
Sort of means, "i could care less...!"
Jackie: Oh my god! I just
broke a nail!
Bec: Nnnyeh, go write a play about it
Tom: Linda just broke up with me! *sob*
Luke: Why
don't you write a play about it?
Ally: You forgot my
birthday! I feel so hurt and let down.
Harry: Yeah, get out some paper and write a play about it.