Kid: Mum, how do you know someone is drunk?
Mum: See the four birds over there?
Kid: Huh, wait a minute.
Mum: A drunk person would see eight.
Kid: Mum, but there is only two.
Kid: Mum, how do you know someone is drunk?
Mum: See the four birds over there?
Kid: Huh, wait a minute.
Mum: A drunk person would see eight.
Kid: Mum, but there is only two.
The humor comes from the kid's unexpected response. The mom is trying to use the classic sign of being drunk - seeing double - but the kid sees only two birds when the mom implied four, making it clear the mom is the one who's drunk.
Big Pimp Jit
THE KID WAS DRUNK
Shade
there was actually 1 bird