"A change is going to come..."
Doctor Who: The Time of the Doctor - Easter Eggs & Hidden Details
Easter Eggs
A brief reference to the Doctor having an 'android boyfriend.'
During a phone call with Clara, the Doctor mentions an 'android boyfriend.' This is seen by some fans as a nod to the non-canon animated web series "Scream of the Shalka," where the Doctor's companion was an android version of the Master.
The children's drawings in the Doctor's room.
The drawings on the wall of the Doctor's home in the clock tower depict his various adventures and companions, specifically recalling the drawings made by a young Amelia Pond in "The Eleventh Hour," bringing his story full circle.
The Doctor mentions his 'vanity issues' regarding a past regeneration.
When explaining why he has no regenerations left, the Doctor refers to the Tenth Doctor's regeneration into himself in "Journey's End" as being due to "vanity issues." This is a direct reference to David Tennant's Doctor using regeneration energy to heal himself without changing his appearance.
The Twelfth Doctor's first lines reference his new kidneys and his inability to fly the TARDIS.
The focus on a specific body part (kidneys) is a humorous callback to the Tenth Doctor's obsession with his "new teeth." His immediate struggle with flying the TARDIS harks back to the very beginning of the show, positioning the new, older Doctor as a fresh start, almost like the First Doctor all over again.