Despite Molly's invisibility, the characters still track her movements and make direct eye contact. They even react to her motions, like high fives and hugs, without verbal prompt.
Alex Désert played Eli Williams on the sitcom Incorrigible Cory (1993), whereas Rowan Blanchard is the star of the Boy Meets World sequel series Le Monde de Riley (2014). Désert played Cory Matthews' teacher and Blanchard plays Cory's daughter, Riley.
Paris Berelc is the fourth actress from a Disney XD series to star in a Disney Channel Original Movie, after Kelli Berglund in Le Garçon idéal (2014), Spencer Boldman in Zapped : Une application d'enfer ! (2014), and Olivia Holt (prior to starring in I Didn't Do It (2014) on Disney Channel) in Skylar Lewis: Chasseuse de monstres (2012).
Based on the novel "My Invisible Sister" by Beatrice Colin and Sara Pinto.
Coug originally had a younger sister named Karen (Francesca Capaldi). Why she wasn't featured in the final film is not known.