Gato por liebre literally means "cat for a hare." It's a fantastic Spanish idiom for being tricked or deceived, like someone trying to pass off something inferior (a cat) as something more valuable (a hare).
In the song, it's part of a mother's warning to her daughter about people who might try to fool her in life and love. This clever phrase perfectly captures the song's central theme of suspicion and not taking things at face value.
Picture this classic late-night drama: it is three in the morning, someone is sitting awake staring at the door, and their partner is nowhere to be found. In "3 A.M.", Joy (from the Mexican sibling duo Jesse & Joy) kicks things off with a piece of advice straight from her mother: "Hay quien te vende gato por liebre" (literally 'There are those who sell you a cat for a hare', an everyday idiom meaning someone is pulling a fast one on you or tricking you with a counterfeit). Joy had already warned her partner that she believes in "ojo por ojo" ('an eye for an eye') when it comes to liars. Now, she is pacing the room with an anxious gut feeling keeping her awake: "Son las tres de la mañana y no has llegado / Sé que estás con alguien y lo estás negando" ('It is three in the morning and you haven't arrived / I know you're with someone and you're denying it').
Enter Gente de Zona, who swoop into the conversation with the most audaciously silly excuses you could imagine. Instead of owning up, they hit back with total party energy: "Yo solo estaba con mis amigos tomando tequila en la madrugada" ('I was just out with my friends drinking tequila in the early hours'). And their excuse for losing track of time? "Y el reloj miré / Pero se paró" ('And I checked the clock / But it stopped'). Blaming a broken watch for vanishing until dawn is hilariously bold. The whole track plays out as a lively back-and-forth dispute, contrasting serious suspicion with frantic pleas to "cambia esa cara" ('change that face') and "vive la vida" ('live life'). It turns relationship paranoia into a fun, rhythm-packed showdown.