In Grand Theft Auto 5 , one landmark was visible practically no matter where you were in San Andreas: Mount Chiliad. "Claimed by the Spanish in 1769, Mount Chiliad is the highest peak in San Andreas, sitting at a height of 2,744 meters," reads a sign at the nearby Silent Probe Mountain art installation. "Taken under Mexican control in 1821, it was then, and remains in American hands since 1847."

It's more than just a mountain, though. Once the player has achieved 100% story completion, standing atop the mountain at 3 a.m. during cloudy weather reveals a UFO, hovering in the night sky. It's marked with an F.I.B. logo, aka the Federal Investigation Bureau, implying that it was created by the government. However, there's also reason to believe that the mysterious aircraft is a hoax, because it doesn't react to bullets, and raindrops nearby become pixelated.

The running theory is that it's a hologram, as opposed to the two other functional UFOs in the game, which are physical objects.…