HiFi

HiFi was the stuffed panda mascot of Steven Taylor, who grew very fond of him during his two years of isolation on Mechanus. During the fire in the Mechanoid City, Steven risked his own life in order to rescue him. (TV: "The Planet of Decision") Steven took HiFi with him in the Doctor's TARDIS. (TV: "The Watcher")

HiFi was given as a gift to Bobby Zierath, (PROSE: The Schoolboy's Story) who returned HiFi when he grew up, and HiFi remained on the TARDIS even after Steven's departure. (PROSE: The Three Paths)