It’d be very difficult not to mention Lassie when talking about the Collie. So there. LASSIE. Now that that’s out of the way, the Collie is a very popular breed of large dog, not only for its obvious ties to classic literature and film, but for its sharp mind and friendliness. This loyal pooch rarely show signs of aggression, unless, that is, its owner is in need of protection. Equally fearless and gentle, the Collie makes families happy.