A man walks into a bar with a dog and a cat. The bartender tells him, "We don't allow animals in here, buddy." The man responds, "But these are very special animals. They're knot theorists." The bartender is skeptical. "Oh yeah? Prove it." He looks at the cat. "Name a knot invariant." "Mu! Mu!" He looks to the dog. "Name a knot invariant." "Arf! Arf!" The bartender kicks the man out. Out on the street, the dog looks at the man and says, "Should I have said 'the Jones polynomial?'"