Trailer
A trailer (also known as a preview) is a commercial advertisement, originally for a feature film that was going to be exhibited in the future at a movie theater/cinema, but has also been attributed to television shows as well as video games and other sorts of content material for the brand. It was a product of creative and technical work.
Trailers have been a part of the Doctor Who franchise from the very beginning in 1963 as small snippets of the show, and has continued to be part of the show to this day. Trailers varied from anything between 30 seconds and 2 minutes.
In the early days, the BBC would air a single simple trailer just to give away the basics of what the audience was going to get in from a story. In the 21st century trailers have been anything from the action of the story to specially filmed content just for the trailer, even entirely new narratives. The amount of trailers were also changed. Trailers could differ between being set in the "DWU" and being out-of-universe.
Next Time
Since 2005 revival of Doctor Who, episodes have typically ended with "Next Time" previews for those that would follow, with this trend passing on to the televised spin-offs Torchwood, The Sarah Jane Adventures and Class.
Initially, the end of the episode was immediately followed by the Next Time trailer which was itself followed by the closing credits. This practice garnered some controversy early on in Series 1 when Aliens of London [+]Loading...["Aliens of London (TV story)"] ended with the Ninth Doctor in mortal peril at the hands of the Slitheen only for the trailer for World War Three [+]Loading...["World War Three (TV story)"] to immediately reveal his survival. From then on, the previews of certain two-part adventures were pushed back to follow the end credits where appropriate.
Series 2's Rise of the Cybermen [+]Loading...["Rise of the Cybermen (TV story)"], which ended with the Tenth Doctor and his companions facing the threat of deletion from the Cybus Cybermen, had no Next Time trailer at all for The Age of Steel [+]Loading...["The Age of Steel (TV story)"], with the closing titles opening with "To Be Continued". Similarly, Series 4's The Stolen Earth [+]Loading...["The Stolen Earth (TV story)"], which ended with the Doctor starting to regenerate after being shot by a Dalek, had no preview for Journey's End [+]Loading...["Journey's End (TV story)"].
The first three series finales ended with no preview, only a promise that "The Doctor will return in" the following Christmas special. The Christmas specials themselves were followed by "Coming Soon" previews for the first half of the upcoming series.
Doctor Who: Unleashed the behind the scenes spin-off accompanying Doctor Who beginning in 2023 offered exclusive clips from upcoming episodes.
