Continuity mistake: When the Doctor leans on the railing above the glacier while telling Adelaide about the Ice Warriors, he rests his left hand a ways out on the railing, in a spot where it should be visible but isn't in the next shot from behind him. (00:28:57)
Continuity mistake: When Gadget is driven to the TARDIS so the Doctor can retrieve it, the landscape around it is much flatter and without the large boulders strewn around the TARDIS when the Doctor arrived on Mars at the beginning. (00:52:41)
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man
Season 2: The Well.
jakew25