Little Johnny is sitting on his front porch...

stirring a bucket of chicken shit. After a short while the milkman walks up for the morning delivery and asks him what he is making.
"A milkman", little Johnny replies.
Puzzled the milkman leaves.
Soon after the mailman walks up and asks little Johnny the same question to which he replies
"I'm making a mailman!"
Shaking his head, the mailman walks off.
That afternoon the milkman and the mailman are having lunch and discussing little Johnny's latest antics and are overheard by a cop who decides he wants to see this for himself.
So he goes over to little Johnny's and sure enough, there he is still sitting on the front porch stirring his bucket of chicken shit. The cop goes over and asks him the same question-
"what are you making there Johnny?'
Little Johnny responds, "a milkman and a mailman!"
Confused the cop asks, "why dont you make a policeman?
Little Johnny replies, "I dont have enough chicken shit!"