Bush baby

A bush baby was a small mammal. When the First Doctor, John and Gillian visited a zoo on an unnamed planet, the zookeeper was given to walking around with a bush baby on his shoulder. Finally, Gillian could no longer resist the fluffy animal, so she asked the keeper if she could walk around with it for a while. He — and the bush baby — agreed. (TVC: The Didus Expedition)

Behind the scenes
The comic actually calls the species "bush baby" and not one its other names, like galago.