The End of Time: Part Two - S4-E18
Deliberate mistake: When the Doctor visits all his recent companions before he regenerates, he goes to a book signing of A Journal of Impossible Things, written by Joan Redfern's great-granddaughter. When she is signing the book for the Doctor, you can hear the scratching effect from the pen but you can see that the pen isn't touching the paper. (00:59:50)
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man