A title sequence is that part of a programme which, typically, gives the series title, theme music, serial or episode name, and may also provide the names of the principal actors involved, as well as that of the writer.
Historically, the title sequence has been of great interest to Doctor Who fans, especially when it has been overhauled, as at the beginning of a new actor's tenure as the Doctor, or simply when a producer decided to do so. Changes to the title sequence can be rigorously scrutinized by fans, who may be interested in such minutiae as the font used in the title cards, or even relatively minor variations in the theme music.
The 1963 - 1967 version of the programme titles did not feature an image of The Doctor, but from 1967-1989 the title sequence included a shot of the current Doctor's head floating either through space or the time vortex, a popular feature which some fans would like to see resurrected in the BBC Wales version. However, the presence of the head — or in the case of Season 11, the body —of the Doctor during the Troughton, Pertwee and Tom Baker eras rendered the title sequences more abstract. John Nathan-Turner's radical redesign of the title sequence completely eliminated the time vortex, and replaced it with a representation of space that was never seen in that way within the body of episodes — mainly because the visual effect of space was far more advanced than what the production team were able to produce on a weekly basis.
By contrast, the title sequences used during the Hartnell era, the McGann telemovie, and the whole of the BBC Wales era, were not abstractions, but showed the time vortex in a way that was used within the body of stories themselves. (DW: An Unearthly Child, Doctor Who, Utopia, The Pandorica Opens)
The first three title sequences feature electronic "howlround" on a plain black background.
From the Third Doctor's last series and almost all of the Fourth Doctor's featured a "slit scan" made to look like a time vortex.
From the Fourth Doctor's last series to the Sixth Doctor's last series features a "starfield".
The Seventh Doctor's title sequence was computer generated and purple.
The Eighth Doctor's was similar to the Fourth's, using the "Tunnel Effect".
This was very similar to the Eighth's, with a red vortex and a blue vortex.The TARDIS moved more vigorously in the red one like in the 2010 version.
This one was similar to the previous, but using storm cloud and lightning effects as the vortex, culminating with a fiery one with no lightning. In the fiery vortex, the TARDIS seems to move much more vigorously.
The howlround titles from 1963-1973 and the slit-scan titles from 1973-1980 were created by Bernard Lodge.
The animated starfield titles from 1980-1986 were created by Sid Sutton.
The computer generated titles from 1987-1989 were created at CAL video.
This short intro started with the word Torchwood on the wall of the Torchwood hub and consisted of red lines and the red coloured word Torchwood in various shapes, sizes, fonts and order on a black background and ended with simply the word Torchwood in the middle.
The Sarah Jane Adventures
This title bore resemblence to the 2005-2009 titles but with letters instead of the Time Vortex effect.
K9 and Company
This title had a science theme, starting with graphics of a DNA double helix and the structure of an atom. It then has graphics of K9 Mark 2 being built up and his body labeled.