Your mum

The best phrase/come back/retort/saying etc that anyone on the earth can say.
it's simple and easy to remember.
It never gets old and is always funny in nearly all contexts

Hey wat u doin?
your mum.

are u free on friday?
your mum is free on friday.

wat dya want 4 breakfast?
your mum

y r u so l8?
your mums l8.

y are u sayin 'your mum' all the time?
cos of your mum