Mortal Kombat · Sega Genesis · 1993 · Impact: Industry-Changing
Programmer Mike Boon's hidden blood-restore code — entered on the "Code of Honor" screen to re-enable gore censored by default — became a flashpoint in the 1993 Congressional hearings on video game violence and a direct catalyst for the creation of the ESRB rating system.
When Midway's Mortal Kombat was ported to home consoles for simultaneous release in September 1993, the two major platforms handled content differently. Nintendo mandated that the SNES version ship with all blood replaced by grey "sweat" and the most graphic fatalities altered or removed. Sega allowed the Genesis version to ship with explicit content disabled by default but restorable through a code. Genesis programmer Mike Boon implemented the code — A, B, A, C, A, B, B on the "Code of Honor" screen, an acronym he derived from a Genesis hardware specification document on his desk — that re-enabled arcade-accurate blood and all fatalities. The code spread almost immediately through playground networks and gaming magazines, was printed in gaming publications nationwide within weeks, and was soon known by virtually every Mortal Kombat player in the country. The existence of this code — and the fact that the Genesis version outsold the SNES version substantially once the code became known — became central evidence in the December 1993 Congressional hearings chaired by Senators Lieberman and Kohl. The argument was not merely that violent games existed but that the violence could be unlocked by any child who knew the code, circumventing parental oversight of the default-censored content. Sega's approach, which had seemed commercially savvy, became a liability in the regulatory debate. The hearings gave the industry a six-month ultimatum: implement a ratings system or face federal legislation. The Entertainment Software Rating Board launched in September 1994. A hidden code entered by millions of children had contributed directly to the creation of the most significant content-regulation infrastructure in gaming history.
Senator Joseph Lieberman's staff had prepared video footage of Mortal Kombat fatalities for presentation to the committee — footage taken from the arcade version and the Genesis version with the blood code active. The contrast between this footage and the SNES version's neutered content was presented as evidence of an unregulated market in which harmful content was freely available while parental guidance was easily bypassed. The blood code was specifically cited as a mechanism that allowed children to access content their parents believed had been appropriately regulated by the platform holder's censorship requirements.
This argument was effective precisely because it was accurate. The code had been in every gaming magazine by November 1993. It required no technical skill. A parent who purchased the default-censored Genesis version would have been unaware that their child could restore all content within minutes of turning on the console. The code transformed a policy decision — Sega's choice to censor by default — into evidence of a loophole, and the regulatory response addressed the loophole by requiring visible content labelling before purchase rather than relying on platform-level default settings.
The ESRB system that emerged from the Mortal Kombat controversy established a labelling framework that persists largely unchanged into the present. Ratings categories — EC (Early Childhood), E (Everyone), T (Teen), M (Mature 17+), AO (Adults Only) — were applied to games before retail distribution, with content descriptors explaining specific concerns. The system was voluntary in legal terms but functionally mandatory because major retailers agreed not to stock unrated games.
The blood code's indirect consequence was the AO rating's commercial toxicity: retailers' refusal to carry AO-rated titles gave the ESRB soft power over content decisions that extended far beyond labelling. Publishers routinely edited games to achieve M rather than AO ratings, because AO was functionally a ban from major retail channels. This dynamic shaped content decisions in mature-rated games for decades, producing the paradox of a voluntary system with near-mandatory compliance due to market structure rather than legal requirement — an outcome that neither the Congressional hearings' participants nor the ESRB's founders had fully anticipated.