I worked for a movie theater company for 12 years as one of my previous jobs. From experience, I can tell you that some previews are a;ready attached to the movie by the studio when the film arrives at the theater. The theater is not allowed, by contract, to remove them. The movie studios will often hire people to verify which previews are shown prior to the movie and report back. as someone else posted, are you sure the preview wasn't for a PG-13 movie? You should try contacting the studio that produced Mars Needs Moms and mention which previews you saw before the film.