It is common in fiction and reality alike for people to start off with a partner in their professional environment. This can range from perfectly normal careers, to working in stuff like tag-teams and superhero teams -- perfectly normal regardless of situation. This trope is very common in music, and in professional wrestling. See also The Band Minus the Face, Breakout Character, More Popular Spinoff and Ensemble Darkhorse. Contrast with The Pete Best, which is when the left-in-the-lurch character was never closely affiliated with the soon-to-be-famous group to begin with.