Spanish Joke:

¿Cual es el animal mas infiel?
El pato, porque siempre anda con dos patas.


English Translation:

Q: What is the most unfaithful animal?

A: The duck, because it always walks around with two patas

Pata means "foot" or "paw", but would also be the feminine of pato--"duck".

(For some reason, when you ask Mexicanas, "¿ Qual es el animal mas infiel?", the majority say, "¡ El hombre!")