How come there is no Knock-Knock joke about America?

How can you tell if you are allergic to pollen?

How can you get four suits for a dollar?

What runs from one city to another but never moves?

Why are night crawlers so smart?

What do you call a cow who has just given birth?

How can you tell if your dog is lazy?

How do you get down from an elephant?

What do you get when you cross an astronomer and a mackerel?

What sound does a witch’s car make?