You may be looking for the Doctor's nickname or an alternate Doctor.

In July 2016, the Twelfth Doctor joined an internet forum under the name ThetaSigma. He wrote an extremely negative post about an episode of a television series. (COMIC: Planet of the Rude) He had previously been known by the name at the Time Lord Academy. (TV: The Happiness Patrol et al.)

Behind the scenes Edit

The Doctor's name is in reference to the Doctor's nickname while at the Time Lord Academy, Theta Sigma.

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