Johnny Depp returns to the big screen on Wednesday in the John Dillinger biopic, Public Enemies
. Though the film's actors are busy promoting the movie around the world, one star is remaining somewhat silent – because she can't speak! Toula, a 5-year-old border collie, makes an appearance in the movie, greeting Depp and his gangster buddies as they arrive at a remote inn. "It's not a huge part, but it's interesting," says owner and dog trainer Christine Mahaney tells PEOPLE Pets. "It's where the film all changes."
Mahaney, who taught herself to train dogs, entered Toula in PetCo's "America's Most Talented Pet" contest when she was just a pup. After the duo won, Mahaney reached out to several Hollywood agencies, and began training dogs for film. Being a Midwesterner (Mahaney and Toula live in Plainwell, Mich.), she's not near the glitz and glamour of Hollywood. But, when Public Enemies
began filming around Chicago and Wisconsin, Mahaney jumped at the chance to work on-set. "Of course it was a great opportunity for me," she says. "And since Toula was born in a shelter – she's a rescue – it was a really special part of my life."
Mahaney and Toula spent a night on set, shooting their pivotal scene. "It seems easy, but you get 150 people standing around – and factor in that it was filmed at night – and it's hard," Mahaney shares. "But Toula was able to do what was necessary on her commands, and we didn't even have to do one retake!" Mahaney reveals that there are many tricks involved when it comes to dog training for a movie. "You have to make training fun for the dog, and you don't want him to be burned out. Get the dog solid on his behaviors and commands, but also be sure you have a dog that's comfortable in a multitude of settings and environments," she says. "Toula is great when it comes to that."
While filming her spot in Public Enemies
, Toula was among the most popular cast members. "When you arrive on set with the dog, everyone's your friend," Mahaney says. "You get people who have been on set for months at a time, and having the dog around is therapeutic. Luckily, Toula loves people, so if you don't mind dog kisses, she has plenty to give!" Click here to become friends with Mahaney on PEOPLE Pets!Read more about on-set animals:Secret Life Star Has 2 Not-So-Secret Loves: His Rescue DogsEXCLUSIVE VIDEO: Bindi Irwin Shares Whale Tales From Free Willy Set