A fan mod for the game which allowed players to have sex with the character Johnny Silverhand, played by actor Keanu Reeves, was taken down at the request of the game's developer CD Projekt Red as they considered it to be potentially harmful towards those who had lent their likeness.

Despite this, at a promotion for the film The Matrix Awakens, when Reeves was told about it by the Verge, he expressed his pleasure for it.
Contributed by KnowledgeBase
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If the player goes to the bathroom in V’s homestead, three seashells can be found on a ledge by the toilet. This is a reference to the 1993 film "Demolition Man", where in John's bathroom, there are three seashells next to the toilet that replaced toilet paper in the future, yet the film never reveals how they work.
Contributed by ProtoSnake