Twitter

Twitter was a social networking website on the Internet in the 21st century.

By the late 2010s, Twitter was central to news distribution, and even influenced which stories got covered. Rhys Williams believed that "If nobody's tweeting about it, it isn't news these days". (AUDIO: Sargasso)

Information from invalid sources
In a non-spoiler review of Big Show Everyone's Into, there were icons for Facebook, Twitter, Pinterest, and Reddit. (WC: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract)

Behind the Scenes
In an invalid promo for The Day of the Doctor where the fourth wall is broken, Dan Starkey in character as Strax makes an important announcement on behalf of the Sontaran Empire for the apparently preoccupied audience: "Stop tweeting and watch the movie, you pitiful human scum!" This annoyed remark was followed by a comedically timed mood swing from fury to a wry grin at the viewers.

A social media site called "Twitbook", a patiche of Twitter and Facebook, also exists in the DWU.