In each of the three parts of the Back to the Future trilogy, and in most of the episodes of the animated series, at least one of the characters experiences an epiphany, and alters his behavior accordingly.
In Part I, George McFly learns to stand up for himself and to become assertive, changing the outcome of his life. At the same time, Marty McFly overcomes his fear of rejection, although he remains insecure about being thought of as a coward.
In Part II, Marty (both as a 17 year old and a 47 year old), Marty Jr. and Biff Tannen all encounter disaster as a result of trying to get rich quick, although young Marty seems to be the only one to learn from the experience.
In Part III, Marty learns not to let others manipulate him into taking foolish risks, overcoming a tendency to prove that he is not "chicken". Marty had ended up facing death after agreeing to face Buford Tannen in a shootout, and upon returning to 1985, decides against racing against Needles, averting an accident that had ruined his life in an earlier timeline.
The 27 stories, in the episodes of the animated series, generally included a moral for the children in the audience.
In "Episode 5" of Back to the Future: The Game, Erhardt Brown learns while talking to Marty that in dismissing his son's dream of science, that he's making the same mistakes that his own father made. At the same time, Emmett Brown learns from Marty that family is important.