Although many of the Fafhrd stories make a serious point, Leiber's tone is usually satiric. Fafhrd and the Grey Mouser are, above all else, examples of the old "thief with a heart of gold" tradition which dates back at least to Robin Hood, if not to the tricky slaves of Greek and Roman comedy. Although they make their livings by theft and, on occasion, more serious crimes, the two friends almost invariably end up in a morally superior, or, at worst, morally ambiguous position. Their victims tend to be corrupt city bureaucrats, wizards, merchants, or other criminal types who deserve what they get.

If these stories have a single unifying theme it would probably be the virtues of male companionship. Fafhrd and the Grey Mouser are true friends who would quite literally fight Death himself in each other's defense. Although female companions frequently share both their beds and their adventures — Leiber avoids any hint of explicit homosexuality — each man's primary bond is clearly to the other.