Bio: Harry Sullivan was presumably a long-serving member of U.N.I.T. before he was introduced to Doctor Who audiences in the Fourth Doctor's first serial, "Robot". He certainly had worked long enough at U.N.I.T. to earn the Brigadier's trust to watch over the Doctor in his first few post-regenerative hours. He took the job a little too close to heart, though, and ended up being lured into the TARDIS and far away from his U.N.I.T. duties.
He was shown to be a bit of a bumbler next to his more experienced TARDIS travelers, perhaps owing to a youth with his head in the books and adulthood spent following orders. He frequently sparred with Sarah Jane over his somewhat antiquated views of gender roles. Thus he was a foil for both the Doctor's casual competence and Sarah Jane's ardent feminism.
HIs inclusion in comic strips is somewhat problematic as all the serials in which he was seen are fairly firmly connected by a single narrative arc. Works which feature him can only be read as canonical if you believe Harry and Sarah rejoined Harry following "Terror of the Zygons", Harry's televised swansong.