10 Things Everyone Always Gets Wrong About Doctor Who
3. Tasha Lem Was Supposed To Be River Song
Tasha Lem's debut in the 2013 Christmas special The Time of the Doctor brought with it immediate, understandable comparisons to River Song.
With both characters having a history with the Doctor, both having the same fun, flirty relationship with him, and both being capable of flying the TARDIS, there was enough evidence to suggest that Tasha might've been an incarnation of River, or, as some fans believe, was originally meant to be River, only for the character to be changed as the episode entered production.
Despite the belief that Tasha is River (or was supposed to be River) being raised on various forums over the years, it simply isn't true. Steven Moffat has said that he was aiming for a different kind of relationship with Tasha and the Doctor, though he did also admit that he perhaps went "a bit too River Song":
"What I was looking for was, it was like the Doctor meeting his first girlfriend... so they have a certain knowledge of each other, but it's from a long time ago, and they're at ease. I think it went a bit too River Song, because everyone loved River so they sort of made her into another River."
All of the "evidence" in the episode can be easily explained away, and though it's a cool theory, Moffat's comment strongly indicates that Tasha - though admittedly similar to River in some ways - was always intended to be her own character.