Some Spanish expressions cannot be taken literally. It's one of the reasons why it is sometimes difficult to translate what people mean when they speak to you.
El horno no está para bollos Lit. The oven is not ready for buns. It means you're not in the mood for any nonsense.
¡Vete a freír espárragos! Lit. Go off and fry asparagus. Basically disappear and do whatever you want as long as it is out of my sight!
Pagar un ojo de la cara Lit. To spend an eye in your face. To spend "an arm and a leg".
Tener mala leche Lit. To have bad milk. To be very bad tempered.
Empinar el codo Lit. To straighten up one's elbow like a pine. To have quite a few drinks, referring to your arm's position when drinking.
Guay del Paraguay Lit. Cool from Paraguay. As cool as it gets - a silly rhyme that reinforces the idea of cool.
Estar como unas castañuelas Lit. To be like some castanets. To be very happy.
Tener un cacao mental Lit. To have cocoa in your mind. To have your mind in a mess. Cocoa needs a lot of stirring, hence the feeling in your head.