I like these ....

you can’t teach an old dog new tricks loro viejo no aprende a hablar
You know what a loro is - think Loro Parque ... an old one won´t learn to speak/talk

talk of the devil …(and the devil appears) hablando del rey de Roma....... (y él que se asoma)
(okay, who's good on history as to why it is the King of Rome?)

Rome wasn't built in a day no se ganó Zamora en una hora.
(I think we need a thread on Spanish history - Zamora was a battle, not won in an hour)