In Doctor Who he played the part of Jamie McCrimmon, a companion of the Second Doctor, from 1966 to 1969 as well as reappearing in The Five Doctors (1983) and The Two Doctors (1985).
Hines appeared in more episodes of Doctor Who than any other actor playing a companion in the series. The only actors appearing in more episodes are those who played the first four Doctors. During the 1960s the show had a much higher episode output than in the 1970s and 1980s, so Hines was in more episodes than some later Doctors. Many of the episodes featuring Hines are now lost, due to wiping of the black and white period of the series.
Hines released a novelty record entitled "Who's Doctor Who" during his tenure in the series. Released on the Major Minor record label, it didn't chart.
He had to leave the show after his agent decided he didn't want Frazer in the show. Frazer left at the same time as Patrick Troughton, who had to leave due to similar circumstances (his wife disapproved of the show).