"One of the requirements that I wanted from Lis was that she had big tits," Lucía Alemany said in reference to the the main character. "Because there is something there, in that 'two days ago I was a girl, and right now I have something that is sexually super attractive'". Finally the girl chosen for the role was the 15-year-old Carmen Arrufat.
Carmen Arrufat said the situations that Lis goes through are far from her reality. She didn't even understand them. Asked what was the most complicated, she said, "The phrase 'I'm pregnant.' Lucía (Alemany) fought hard so that she could say it naturally, but in my head there is no possibility of getting pregnant, much less with 15 that I was then. It was a complex situation that cost me a lot."