The Doctor Who Internet Adventures come from a unique period in the history of Doctor Who. The 8th Doctor possesses only a single television adventure to his credit from which people could draw their cues on the character. Never before or since has there been such a loose control over the definition of a Doctor's character, and as such no concrete sense of the one true narrative prgression. Multiple canons and continuities across opposing media — books, comics, audios — have sprung up, each clamouring for fandom's attention as the 8th Doctor's standard bearer.
Thanks to the decades of often wildly independent comics and the episode novelisations that predated any notion of the series being released on video, Doctor Who fandom has always possessed a distinct literary and literate streak. In the absence of the orthodoxy of an ongoing television series, this streak was further nurtured by 5 years of the New Adventures (the ongoing story of the Seventh Doctor) and Missing Adventures, (stand-alone adventures of the previous Doctors). Apart from two attempted spin-off stories released by Target in the 80s, the idea of original novels based on the series was startlingly new, especially the degree of interactivity that came to exist between the audience and the producers as more and more fans became the new creators of the series. Virgin's books were an unexpected success; in fact, they may have been too successful, as the BBC used the changeover from the 7th to the 8th Doctor as the oportunity to reclaim the novel licence, intending to make the literary aspect of Doctor Who their own cashcow. Part of this process included the announcement that the BBC would not accept unsolicited manuscripts, thwarting the hopes of countless fans that they too might be able to help tell the ongoing story of their hero in a way that mattered.
Another significant factor to the success of the Internet Adventures in tapping the Zeitgeist was the larger context of when they took place. The change from McCoy to McGann and the resultant failure to launch a new series happened just as the world at large was discovering the Internet. Prior to this, fandom had been an essentially localised phenomena communicating through group meetings and print fanzines, the output of which were idiosyncratic and slow as zines were dependent on both the ability of the editor to afford to put an issue out and having enough material to assemble one in the first place. And while it was possible to access fanzines from outside your own geographical location, you had to be able to afford a subscription, which presupposed an awareness of a zine's existence to begin with. The BBS network was little better, again fettered by the tyrannies of long distance charges and visibility to the wider world. But once someone passed the singular hurdle of gaining access to the 'net, it became essentially trivial for global fandom to interact in a speedy manner in central locations. It became possible for Americans, Australians, Canadians and Britons to collaborate on a single project and do so effectively, for little if any direct cost.
What became known as the Internet Adventures (named for the original line of Virgin novels) began on the alt.drwho.creative Usenet group as an exercise in collaborative fiction — specifically, a round robin story, run by a moderator who also participates in the writing — amidst the hype surrounding the much anticipated 1996 telemovie, which paired Paul McGann's altogether dishy Doctor with surgeon Grace Holloway.
DeathRace's first chapters pre-empted the broadcast, and was based on the assumption that Grace would be leaving Earth in the Doctor's company at the end of the telemovie. Even though that turned out not to be the case, Grace — and more importantly, that first story itself — were popular enough with everyone that the ball kept rolling. From that point, they took on an existance of their own: Grace was eventually supplanted by a new traveller (who was in some respects arguably an avatar of his fannish origins and was certainly the longest serving of the Doctor's internet companions) who was in turn joined and replaced by other characters and other inspirations fed by the infusion of personal fascinations and pop-cultural awareness from the new blood that was constantly stumbling across the Internet Adventures through luck or word of mouth.
Marvelous Chap, All of Them
Soon, what had been the effort of a small number of individuals became a brand wagon; people wanted to be a part of it. This was the final aspect that made the Internet Adventures different from other fanfiction exercises — it was an enduring universe shared with others. People were queueing to agree to abide by what had come before, giving significance to another author's contribution just as others would entrench theirs.
Soon, this collaborative energy could no longer be contained by a single ongoing saga, and it began generating its own spin-offs. Again named for the Virgin novelsr, the Missing Internet Adventures were all about combining the magic of shared universe writing with the equally powerful force of nostalgia. The end result proved almost as enduring as its parent and attracted writers who maybe didn't love the 8th Doctor and his new friends as much as they longed for a lost golden age
Inspired by this, the franchise spread to the post-TARDIS adventures of the enduringly popular companions in the form of the Companion Internet Adventures; stories dealing with the escapades of Professor Bernice Summerfield, though technically a part of this became their own distinct endeavour. There was even an attempt to disprove the TARDIS crews were the pivot around which the universe rotated by telling the stories of inhabitants of it that had never met any of them but still had to deal with the world they created in the Whoniverse Internet Adventure. And finally, the X-over Internet Adventures indulgently brought the TARDIS crew into contact with other fictional settings.