During the song "Bossa-Nova Junto a Ti", when Marisol and Mariluz are singing and dancing, they're usually featured in a split-screen effect or with a stunt actress with her back to the camera. However, there is a moment when the Marisol character turns around and looks at the camera, and the face of the stunt actress is clearly seen for a second.
When Marisol and her mother leave the appliances store on the run, camera moves to a scene with a couple of fiancees heavily arguing, in this scene there's a window in the background that shows the outside, where it can be seen how Marisol and her mother (the actresses thinking they were out of view) stop running and start waiting for the scene to cut.