In the remote Roanoke Valley area of Red Dead Redemption 2, a man can be encountered sitting alone on a hill, staring at a pocket watch. If approached and spoken to, he describes himself as a time traveller, explains that the device allows him to move between time periods, and demonstrates it by blinking out of existence while Arthur watches.
The encounter is entirely optional, occurs only at a specific time of day, and produces no reward. Arthur’s dialogue options allow varying degrees of engagement with the man’s claim. The man does not reappear.
The NPC has no name in the game’s data. His pocket watch model is the same as the standard pocket watch used by other NPCs. There is nothing mechanically special about the encounter beyond the triggered disappearance animation.
Rockstar included the Time Traveller as one of dozens of unexplained stranger encounters distributed across the map — encounters designed to suggest a world that processes events beyond the story’s awareness. The stranger mission system gives some of these a resolution. Others, like the Time Traveller, simply occur and end. Whether the man is genuinely a time traveller, delusional, or a person pulling a trick on a passing cowboy is left entirely to the player.

The attention to detail the developers put into this is insane. Most players will never see it but it makes the world feel so much richer.
This is the kind of discovery that keeps communities alive for years. Well documented.