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 Chase) Steven took HiFi with him in the Doctor's TARDIS. (TV: The Time Meddler)

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

Behind the scenes

 * Paul Magrs' story The Runaway Hi-Fi explains that HiFi left the TARDIS during the Second Doctor's trial in The War Games and met Iris Wildthyme, becoming Panda. That story was later published in the charity anthology A Second Target for Tommy in 2018 by Obverse Books.