After waiting several hours for the plumber to arrive the homeowner decides to make a quick dash to the store in hopes of returning before the plumber arrives...

...and as he turns the corner; the plumber walks up to his house and knocks on the door. The parrot says "Who is it?" -- and the plumber says "It's the plumber..."

After not hearing a response, the plumber knocks again and of course the parrot asks the same question... and this is going on repeatedly up to the point where the plumber is pounding on the door over and over, again, as the parrot keeps asking who is it...

...and finally the plumber has a heart attack and drops to the ground just seconds before the homeowner returns seeing someone on the ground before his door and he says as he approaches...

... "I wonder who this is"