In August 2007, Paramount Pictures needed an emergency replacement German Shepherd after the original one that they'd cast wasn't fulfilling what they needed. The producers hired Sarah Clifford who brought in Sadie. In the scene, Sadie portrays a nightmare hallucination who appears in the back of a guy's car. As the dog attacks him, he is so terrified that he shoots himself in the head to make it stop.
As anybody who knows Sadie can attest, she is the sweetest dog who wouldn't even hurt a kitten, so this scene was all done through movie magic.... She was covered in make-up, a rubber band on her muzzle made her bare her teeth, and she wasn't lunging at the actor but at a tennis ball hidden by his shoulder. Just add sound effects and scary music to complete the effect.
The movie stars Renée Zellweger, Ian McShane, Bradley Cooper, Cynthia Stevenson, and Adrian Lister. Also, Sadie appears in this trailer at timecode 01:59.