Don´t look at horse´s mouth... en Venezuela se dice a caballo regalado no se le mira colmillo...

Those are very nice jokes. I laughed a bit. I am still slowed down in the understanding of English and American jokes but it is getting better and better along with my language improvement)

So it was really nice to find myself laughing when I was reading those jokes. Thank you

Don't looking the horses mouth it is a quote very useful in Brazil. However, I think it is most common when someone has to accept a gift, just because she

 or he is polite.