A man walks into a bar with a dog. The bartender says "Hey buddy, can't you read that sign? It says no dogs allowed! Get that mutt outta here!" The man replies "No, I can't read the sign - I'm blind, and this is my seeing eye dog". The bartender is very flustered, and gives the man a beer on the house as way of an apology.
So later that day this guy is telling his friend about it - "I told him I was blind and I got a free beer!". And the friend takes his dog into the bar and sits down, and the bartender says "The sign says no dogs allowed! Get out with that thing!" The friend says "I can't read the sign, I'm blind and this is my seeing eye dog." Bartender replies "Since when do they give out Chihuahuas as seeing eye dogs?" The man says "They gave me a Chihuahua?!!?