CNN —“Doctor Who” fans were drenched in nostalgia after David Tennant reprised his role as the Time Lord in the dramatic conclusion to the show’s BBC centenary special. Sunday’s 90-minute episode of the long-running sci-fi show, titled “The Power of the Doctor,” ended with Jodie Whittaker’s character unexpectedly regenerating into Tennant in her final appearance as the 13th Doctor. “I know these teeth,” Tennant said – a reference to the 10th Doctor’s first words – “New teeth… that’s weird” – back in 2005. Sophie Mutevelian/BBC/IMDB“Omg, David Tennant back as the doctor, best regeneration ever,” one person wrote on Twitter. “If you thought the appearance of David Tennant was a shock, we’ve got plenty more surprises on the way!” said showrunner Russell T. Davies in a statement.

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