The End of Time: Part Two - S4-E18
Revealing mistake: When Addams is telling Rossiter not to respond the Master's message, a patch of non-green skin can be seen on her face showing where the makeup wasn't fully painted on. (00:27:50)
The End of Time: Part Two - S4-E18
Revealing mistake: When the Doctor is being rolled down the stairs whilst he is strapped to the chair, it is apparent that in the wide shots, it is a dummy in the chair and not the Doctor. In the wide shots, the Doctor is sitting virtually still and motionless, but in the closer shots, he is fidgiting.
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man