It's one of those days for Daniel Hillard (Robin Williams). First he gets fired from his job, then he gets fired from his marriage, pretty much for the same reason: the man has a passion, verging on the unreasonable, for protecting and nurturing children, and it makes more sensible people crazy.
His job is to supply the voices for a Sylvester-and-Tweety type of animated cartoon; he loses it when the villainous cat forces the victimized bird to inhale a cigarette and Daniel insists on improvising antismoking dialogue for the sequence, so that kids in the audience clearly understand the full horror...