"Seeing Eye Chihuahua" joke

Man with a German Shepherd dog goes into a bar and sits down at
the counter. Bartender says, "You can't bring that dog in here!"
Man says, "But this is a Seeing Eye dog!" Bartender says "Well, OK,
then I guess it can stay."
After a while, the man and the German Shepherd get up to leave. As
they're going out the door, another man with a Chihuahua is coming
in. First man says, "The bartender won't like you bringing that dog
in here, but just tell him it's a Seeing Eye dog and then it'll be
OK." Second man looks dubiously at his tiny Chihuahua, thinks
a fews seconds, then thanks the first man and goes on in.
Bartender says, "Hey! You can't bring that Chihuahua in here!" Man
stares straight ahead and exclaims "What! They sold me a Chihuahua?!"