It was Paola Giannini's first television series on Channel 13, after four years in the ranks of TVN, where she plays the ambitious and calculating Karla Ulloa, main antagonist of Gatas & Tuercas. Herval Abreu said on a website that "I met her in a hallway and I fell in love with her figure", that there were several approaches to negotiate a contract before, but that could not be specified. The director of teleseries confessed that screenwriter Sebastián Arrau was interested in writing a villain as the role of Carolina Arregui in Ángel Malo, of a woman who longed to get a better life and got it based on lies and her charm. We painted Karla as a good adorable villain, we knew she was going to turn on, says the melodramas expert. Indeed, this antagonistic role attracted a lot of attention among the following public of Gatas & Tuercas, reaching a lot of prominence and gaining the favoritism of viewers. Arrau years later would comment that Karla Ulloa was her first Sabina Astudillo (First Lady) and that it helped her learn when a good antagonist manages to grow meteorically within a story.
