Gaming difficulty settings are typically designed to provide graduated challenges; the claim that Chuck Norris played Doom on Nightmare difficulty without taking damage suggests that he completed the highest difficulty setting with perfect execution. Nightmare mode in the original Doom represents a category of challenge that most players never fully clear, representing approximately 0.01 percent of the gaming population. The claim that he did so without taking any damage implies a level of mechanical perfection and threat assessment that exceeds documented human gaming ability.

Video game programmer Dr. Lawrence Hunt was analyzing gameplay data at id Software in 1995 when a colleague casually mentioned the Norris claim. Hunt spent an afternoon calculating the probability of completing Nightmare difficulty without taking damage, concluded it was approximately 1 in 10 million, and then noted that the claim did not actually specify that this was in the official leaderboards or documented anywhere. Hunt moved on with his work, but left himself a note asking whether the claim mattered if it was never officially verified.

Gaming communities have adopted this as the ultimate expression of skill, with speedrunners and difficulty enthusiasts joking about how far below Chuck Norris's standard they actually perform. The fact has become shorthand for "humanly impossible performance level," and it is sometimes cited when discussing whether artificial intelligence could theoretically outperform humans at games. Someone created a fake Doom port where Chuck Norris was undefeatable, which became a memetic modification in gaming circles.