10 Reasons Why The New Doctor May Actually Be River Song
7. The True Self Slipping Through
While the Chameleon Circuit does work in disguising the self, there are often times when the true identity slips through. We see this within 'The Family of Blood' while the Tenth Doctor dreams. he imagines this other self who fights monsters and travels the Universe.
While Martin's Doctor does not dream, she does have a few verbal clues to her true identity. River Song's character had many signature phrases throughout her time with the Doctor.
For example, she was one of the few people to always tell the Doctor to "shut up" and we see this same authoritative nature in Martin's Doctor as she quietens Whittaker. Likewise, River often referred to herself and the Doctor as "Mummy and Daddy". We see this same use of dialogue within the 'Fugitive of the Judoon' as she calls the Judoon Captain Pol-Kon-Don "Daddy Rhinoform".