There's these 3 girls (blonde, brunette and redhead) who walk into a bar and then a cop comes in and realized they were all under age so they all ran into an alley outside.

In the alley there were 3 trash bags.

The policeman comes out and the kicks the first bag (where the brunette was) and she says 'meow'. The officer says 'oh it's just a bunch of cats'.
Then he kicks the next one where the red haired girl was hiding and she says 'woof woof'. The officer says 'it's only a bunch of dogs'.

Then he kicks the last bag where the blonde is hiding and she says 'potato's potato's.'