It is a truism in narratology that characters are effects of the demands of the narrative: it isn't so much that stories are about character's doing things as a series of events that require agents to get them accomplished.
This is the case in all narrative, whether implicitly popular (or populist) or unfailingly formalist, and Singin' in the Rain is no exception.
The specific attributes of Cosmo, Don, Kathy, R.F. Simpson, and Lina produces an immanent set of relations that allows the more abstract work of the film to be performed. These narrative 'agents' provide the concrete terms of the argument that the film mounts, an argument that is at once a defence of itself and a proof of its own artistic legitimacy.
Created in 1998 by Adrian Miles, details, republished 2006.