What has a dog?
People.
What has a dog?
People.
Listen up, nimrod! This "joke" is playing on the double meaning of "dog". A dog can be an animal, but it can also be slang for "ugly". The joke is pretending to ask what animal people have and then saying people are dogs (ugly). People also have dogs as pets, technically, so both meanings could be applied here. The joke is still stupid.