Human-Time Lord metacrisis
Talk about it here.
The first known instance of a Human-Time Lord metacrisis to take place in the Doctor's life occurred during their third incarnation. Overseer Zim attempted to wipe his mind using a mind thresher. After he thought the Doctor's consciousness had been completely wiped, he placed the human mind of Gruppenführer Hans Vogel inside of his brain. Due to the complexity of a Time Lord mind, however, Zim was unable to completely eliminate all traces of the Doctor's consciousness. This resulted in a metacrisis which threatened to destroy both the Doctor and Vogel's minds. In the end, the Doctor was able to remove Vogel from his mind by sabotaging Overseer Zim's facility. (AUDIO: The Hidden Realm)
The DoctorDonna was an example of a human with a Time Lord consciousness. The Tenth Doctor stated that a Human-Time Lord metacrisis had never happened before because it was unsustainable. Donna had to be reverted to her human self; her brain could not hold such a consciousness. The Doctor erased her mind of all knowledge of him against her wishes. (TV: Journey's End) Despite this, Donna's latent consciousness retained at least some non-human aspects, protecting her when the Master turned the world into copies of himself, specifically preventing her from succumbing to the transformation into the Master and also provided her a defence mechanism that could subdue several copies of the Master with a burst of energy, albeit knocking her out as well. Apparently, it also subconsciously guided her to buy a book for her grandfather, which led the Doctor and him to Joshua Naismith. (TV: The End of Time)
The metacrisis Doctor seemed to be a mixture of the two races. He did not burn up, but only had one heart and could not regenerate. He also showed quirks of Donna Noble, the human with whom the metacrisis had occurred, specifically her urge to argue and say "Oi!". (TV: Journey's End)