Man's Best Friend(2003) (USA) (2004)

A romantic comedy about a man, a woman, and their dogs. Steven Merritt, a research obsessed writer is mistaken for being gay by Rebecca, a young veterinarian assistant. He decides to play along in order to do research for his floundering novel. Steven's outlandish plan inevitably backfires, and hilarity ensues as they fall for each other but are unable to express their true feelings.