My original set of pre-gens for convention games included a couple of characters that did not prove popular. One was a nurse, intended to fill the "support" role that's exemplified by the Stalwart in Doctors & Daleks and that maps to characters on the show such as Rory or (to a lesser extent) Rose, Polly and so on. If I was running Doctors & Daleks rather than DWAITAS that would could well be more popular, but I'm not, and it isn't. The second was a barbarian warrior in the Leela mould, which I think proved unpopular because of the low tech, especially in a game that normally isn't heavy on combat.
So I ditched both of those from the selection and added two new characters to replace them. I've no idea how popular they will prove, but the first of them fills the niche of the investigator now that I've made the private eye more physical since that was the way he usually got played. This time, we have an amateur sleuth, intentionally low on physicality but with observational and problem-solving skills that should (I hope) have an obvious function in any RPG scenario that isn't a straight dungeon crawl. Sarah Jane, as an investigative journalist, is perhaps the closest analogy from the show, at least conceptually (although it's arguable how often that comes into play) although the background details here are very different.