When they get the notion to remake an animated classic into a live action film, Disney is a well-oiled machine. They’ve found varying degrees of success and failure (“The Lion King,” “Cinderella,” “Pinocchio”) along the way, and their latest cartoon-to-real-life adventure “The Little Mermaid” lands somewhere on the better-than-average scale. There are things that work (a scene-stealing Melissa McCarthy as Ursula the Sea Witch), things that don’t (a painfully lengthy run time), and things I never want to see again (the truly dreadful “Under the Sea” number), but the film’s reimagined storytelli...