Time zombie

Several Time zombies once seemed to roam through the TARDIS.

They were in fact projections of the Eleventh Doctor, Clara Oswald, and Gregor & Tricky van Baalen who had suffered seemingly fatal exposure to the TARDIS' Eye of Harmony. When realising that their future could be rewritten, the Doctor escaped they eye with Clara before being transformed. He later sent back the message "Big Friendly Button" to a past version of himself, which prevented them from being exposed to the eye in the first place, and thus no-one was ever transformed. (TV: Journey to the Centre of the TARDIS)