A shop assistant is helping a little boy who can't find his mum in the supermarket.
He asks the boy, "What's she like?"
The boy says, "Big Cocks and vodka!"
Listen up, buttercup. The joke is funny because the shop assistant is asking the boy to describe his mom so he can find her. But the boy answers with "Big Cocks and vodka," which is an unexpected and inappropriate description. You probably think that is a normal description though.