K9 Mark II

K-9 Mark II was constructed by an unknown person and was more or less identical to the original (DW: The Invasion of Time). He accompanied the Doctor and his new friend on their quest to locate the segments of the Key to Time (DW: The Ribos Operation), however the swampy terrain of Delta Magna's third moon made it impossible for him accompany them there. At the conclusion of the quest, the Shadow turned K-9 to his evil will, during which time he assumed a sinister personality. (DW: The Armageddon Factor)

K-9 later lost his voice in a form of robotic laryngitis (DW: Destiny of the Daleks). During the Doctor's next adventure (DW: City of Death) he remained patiently in the Doctor's TARDIS, implying, perhaps that his voice had not yet returned. Subsequently, his voice sounded quite different and remained so for a number of adventures (DW: The Creature from the Pit), however by the time he was vacationing with the Doctor and Romana in Brighton he once more sounded like his familiar self. (DW: The Leisure Hive)

Damaged by the time winds, K-9 Mark II could not cross back into N-Space with the Doctor, so decided to stay behind at the Gateway with Romana, to help her free the remaining Tharils from slavery. (DW: Warriors Gate)