"Bob actually did most of his own work... but we had to stop filming one day because he was constipated... He was growling, and apparently it's because he needed to do what he needed to do. We had to wait for him to do what he needed to do, and then we could carry on... We had to send out for some special cat food." Downton Abbey star Joanne Froggatt on working with her feline co-star in new movie A Street Cat Named Bob.