A man walks into a bar with a yellow Labrador Retriever on a leash. The bartender notices the dog and tells him, "Sorry, dogs are not allowed in the bar." The man explains that it's okay, he's a guide dog and the law doesn't apply in this case. The bartender apologizes and allows him to stay.
Later, another man enters with a Chihuahua on a leash. The first man sees him and warns that dogs are not allowed in the bar but if he tells the bartender it's a guide dog, he'll let him in.
The bartender again says, "Sorry, dogs are not allowed in the bar."
The man also explains that it's a guide dog. The bartender says, "Hold on, you're telling me that a Chihuahua is a guide dog?"
The man, with a look of horror on his face, says, "They gave me a Chihuahua?"