Hombres G turn a medical gadget into a dark little joke. "Marta tiene un marcapasos que le anima el corazón" (Marta has a pacemaker that keeps her heart going), and you don't even have to wind it up, "es automático" (it's automatic). Then it gets weird fast: you can hear its "pataditas" (little kicks), and it's "vivo, creo yo" (alive, I think). The pacemaker is described exactly like a baby.
The chorus goes full horror comedy. The singer just wanted to kiss her, felt a blow in his chest, and "ha salido el marcapasos entre vísceras y sangre" (the pacemaker came out among guts and blood). And the punchline: "Mírale qué ojitos tiene, es idéntico a su padre" (look at its little eyes, it's the spitting image of its father), which is what proud relatives say about newborns. It even plays with the other kids, rips their hearts out and eats them "con tomate" (with tomato). Totally silly, and a fun way to learn diminutives like "ojitos" and "pataditas".