Jasper and Stewart were a pair of twin Fledershrews who took up residence within the TARDIS during the Seventh and Eighth Doctor's lives. They lived in the TARDIS for "a long time," and the Doctor regarded them as old friends. Jasper was the more adventurous and approachable of the two, while Stewart was notably stoic and dutiful.
Though the Fledershrews had the run of the ship. They appeared to have established a permanent residence in a seldom-used annex of the TARDIS' enormous library wing, near the "H"s.
Curious about a new presence in the TARDIS' library annex, Jasper landed on the back of a bookcase and crept along the shelf, trying to catch a glimpse of Carolyn McConnell between the books. When Carolyn pulled out the haematology book directly in front of Jasper and saw him, she screamed, (an understandable response, she was researching Vampires) which caused Jasper to panic and take off. There was much screaming and flapping before the Doctor arrived and plucked Jasper from the air to give him chin-scratchies and pettings with baby-talking to calm him down. He then formally introduced Jasper to Carolyn and released him back to the rafters.
Later, when Sam Jones brought the Doctor back to the TARDIS after being imprisoned and starved by the Tractites, he collapsed and slept for twenty-eight hours. The bats helped watch over him, perching on his recovery bed or cuddling in Sam's lap, and when Sam herself had to sleep, Jasper accompanied her while Stewart remained to stand guard on the Doctor.
- Jasper and Stewart were a retroactive creation of PROSE: Vampire Science, giving names and personalities to the two bats briefly seen in the 1996 TV-movie.
- Jasper and Stewart were established to be twins in Seeing I.
- In Return of the Living Dad (published a year prior to Jasper and Stewart's first appearance) "Jasper" and "Stewart" are the names of two teddy bears that the Doctor and companions won at a festival.
- They are not the Doctor's pets. Rather, an offhand comment by Sam in Seeing I seems to indicate that they are the TARDIS'.