Rats can be trained to act in movies just like cats and dogs, but working with a pack of rodents on a film set requires someone with a lot of organizational skills and a close attention to detail. More specifically, a rat trainer needs to be able to identify a rat's personality, strengths, and weaknesses to be able to cast them in the best possible role. To find out exactly what it takes to train rats for movies, we spoke with Mark Harden, a senior trainer at Animals for Hollywood, who worked with 300 rats on "Bram Stoker's Dracula" and 600 on the 2003 horror film "Willard."