Complete the triangle

A blonde, a brunette, and a redhead are walking by a mall.

A policeman starts running after them, so they start running too.

They come upon 3 sacks and jump into them.

The cop stops and kicks the 1st sack and the brunette says "Meow."

The cop says, "Oh, it's only a cat."

He kicks the 2nd sack and the redhead says "Woof."

The cop says, "Oh, it's only a dog."

Then he comes up to the third sack and kicks it.

The blonde says "Potatoes".

And the cop says "Oh, it's only a sack of potatoes!"

Do you know why the cop didn't catch her?

Because he was a blonde too!