Derek (Survival)

Derek was human who in 1989 was transported to the Cheetah World by a Kitling.

Biography
Derek then found Midge and Shreela two other humans who where being hunted by the Cheetah People. Ace helped them try to catch a Cheetah Person but she failed. Instead they caught the the Doctor. When Ace got infected with the Cheetah Virus she helped them get home. He was Happy that he said "Thanks Doctor, Thanks Ace" unlike Sergant Paterson who just walked away. (DW:  Survival)

Behind the scenes

 * Although he survives in the televison story in the Novel he gets killed by Midge after he gets off the Cheetah World.