Ewen McGregor may not have had the option to buy dog food for a four-legged friend because of problems with allergies.
The Men Who Stare at Goats actor explained that he wanted to take the pooch that he was recently filming with home, but that his wife was allergic to dogs.
While he was shooting new movie Beginners, McGregor fell in love with the rescue dog, Cosmo, who was playing his pet and decided to take him home at the end of the film.
He told BlogTalkRadio: "My first idea with the dog that I discussed with [the director] was maybe we could rescue a dog and use it in the movie and then I'd keep him after because I'd really like to have a dog but my wife is allergic and Cosmo sheds.
"I did find a little rescue dog on the last day of the shoot, called Sid, who's my dog now."
The 40-year-old added that he still sees Cosmo now and again and that Sid is a real member of the family.