Sam Hallett had a YouTube channel about conspiracy theories. Kate Wilson, daughter of famous conspiracist George Wilson, became a YouTube star by debunking her father's theories. (AUDIO: The Conspiracy)
Ryan Sinclair had a YouTube channel called RyanS. After his first encounter with the Thirteenth Doctor, and the death of his grandmother, Grace, Ryan uploaded a video entitled "Hey". (TV: The Woman Who Fell to Earth)
Behind the scenes
In the real world, YouTube is owned by Google.
The Twelfth Doctor title sequence was inspired by a creation of a fan of Doctor Who, Billy Hanshaw. Steven Moffat was impressed with the conceptual opening sequence that was popular on YouTube; liking how original it was, he got in contact with Hanshaw for creating an official title sequence.
The Thirteenth Doctor title sequence was created by Ben Pickles, or "John Smith VFX", who gained notoriety through his popular VFX Doctor Who fan videos on YouTube. He was discovered due to these videos. Before series 11, Pickles provided essential VFX for World Enough and Time and Twice Upon a Time.
The Official Doctor Who YouTube Channel was created on 15 December 2005.
The Doctor Who team has occasionally made use of YouTube as a platform for original content. The Fan Show was exclusively a YouTube series. Doctor Who Extra was also largely a YouTube release, and Access All Areas were put out on YouTube and the Doctor Who website only.
Trailers and clips from Doctor Who episodes are regularly released by the official channels.
A livestream event was held on Doctor Who's official channel on the 20 and 21 July 2019 in celebration of the 20th Anniversary of Big Finish audio stories. The opening story of The Legacy of Time also premiered.