Human-Time Lord Meta-Crisis

A Human-Time Lord Meta-Crisis was the term applied to a hybridized organism that combined the traits of a Time Lord and Human. Only two have been known to exist - the "DoctorDonna" and the Meta-Crisis Tenth Doctor. The DoctorDonna had to be reverted to her human self, as a human brain could not hold a Time Lord's consciousness. This forced the Doctor to erase Donna Noble's mind of all knowledge pertaining to him. (DW: Journey's End). Despite this, Donna still remained half-Time Lord, with that protecting her when the Master turned the world into copies of himself. Apparently, it also guided her to buying a book for her grandfather which led him and the Doctor to Joshua Naismith. (DW:The End of Time)