The Doctor's TARDIS/Other realities
From Tardis Wiki, the free Doctor Who reference
Alternate counterparts of the Doctor's TARDIS existed in other realities.
Parallel universes
Earth-33⅓
- Main article: The Doctor's TARDIS (Earth-33⅓)
to be added
Martha loses her Osterhagen key
A version of the TARDIS existed in one parallel universe. When Martha Jones lost her Osterhagen key, "someone better" got her a key ring the size of the TARDIS. (PROSE: "What If... Martha lost her Osterhagen key?" [+]Part of Time Warped!, Loading...{"namedpart":"What If... Martha lost her Osterhagen key?","1":"Time Warped! (DWA 90 feature)"})