¿De cuándo acá? and Other Rhetorical Questions

In the first installment of Tu Voz Estéreo, our brand new series from Colombia, we hear a conversation between two not very pleasant characters who are planning to steal a guide dog (ಠ_ಠ!) from his blind owner:

Ay, pero ¿cómo y de cuándo acá nos gustan tanto los perros?

Oh, but how and since when do we like dogs so much?

Caption 9, Tu Voz Estéreo - Laura - Part 1
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The idiom de cuándo acá (since when) is a rhetorical question. In Spanish, asking ¿Desde cuándo te gustan los perros? is not the same as saying ¿De cuándo acá te gustan los perros? The first one is a simple question, while the second one is asked in order to create a dramatic effect of surprise, outrage, disbelief, or disapproval:

¿Y de cuándo acá eres mi juez?
And since when are you my judge?

Órale, ¿de cuándo acá tan bien vestidos? ¿Dónde es la fiesta?
Wow, since when you dress so well? Where's the party?

There are different ways to translate the English expression "how come?" into Spanish. As a standalone expression, you can use questions such as ¿cómo es eso? (literally "how is that"), ¿cómo así? (literally "how this way"), ¿cómo? (how), or ¿por qué? (why). It's important to add a special emphasis to the way you pronounce these questions:

No había nada interesante que hacer. ¿Cómo?

There was nothing interesting to do. - How come?

Captions 38-39, Guillermina y Candelario - Una aventura extrema - Part 1
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But when the expression is part of a sentence (for example, "How come you don't know that?") you can use the idiom cómo que (literally "how that") or cómo es que (how is that):

¿Cómo es que no sabes eso!
How come you don't know that?!

¿Cómo que no trajiste nada de dinero?
How come you didn't bring any money?

You could say that by using this phrase cómo que we're simply omitting the verb decir (to say), as shown in this example: