Yes, the John Leeson-voiced tin dog rolled along with the Fourth Doctor for multiple serials, assisted the Tenth Doctor in School Reunion and even stuck around for The Sarah Jane Adventures, too. Fans of the show could come up with his multiple appearances without having to think too hard. But did you know K-9 is not John Leeson's only role on the show? In Series 16, Leeson finally got to show his face in The Power of Kroll. Here he played Dugeen, a crewmember of the methane refinery on Delta III. Dugeen knows what they are doing negatively affects the planet's Swampies and when his boss Thawn threatens to exterminate the entirety of the Swampie population, he intervenes. This earns him a bullet to the chest. Well, being a tin dog isn't so bad, right? K-9 earned him fan favourite status, much like the next entry on our list...