Acting for Two: Happens several times. They don't use special effects: each character by the same actor is filmed separately. When they "met", we see rapid shots of each one at the same room, but none with both at the same time.
Martín Quesada was victim of a thief that made up a mask that resembled his face. This thief had sex with Constanza and Esperanza, stole jewels from a museum and killed a guard. Martín Quesada was blamed for this, until he captured the thief.
There was a russian princess that was exactly like Esperanza (just a cosmic coincidence). A good chance for actress Natalia Oreiro to practice russian.
Quique has a really ugly "sister"
Falucho has a brother from Paraguay, who falls in love with Kimberly. Falucho dresses as his brother and have sex with Kimberly, to attack his brother... and he falls in love with Kimberly himself.
During the carnival at the conventillo, Martín dresses as Zorro, and he escapes he is seen by Constanza and Debbie. "Did you recognize him?" "Yes, that was Padre Coraje" (a former character of Facundo Arana)
When needing to get into a slum searching for a killer, Esperanza dressed like "Cholito", a former character of hers from MuñecaBrava. Martín points that she resembles someone he knew (because Facundo Arana was part of that telenovela as well).
When Falucho defied Alfredo to a duel, Miguel boasted Alfredo that he was not a man of honour (in reference to the telenovela Hombres De Honor).