While “SpongeBob SquarePants” is about an underwater sea creature and all his silly antics, “Fifty Shades of Grey” is an R-rated erotic romance movie based on a book by the same name.

MetroLux 14 theater in Loveland, Colo., accidentally showed the beginning of the R-rated film Fifty Shades of Grey to an audience of parents and children awaiting The SpongeBob Movie: Sponge Out ...