The Possessed Docktug is a proven myth in Grand Theft Auto V. It was first revealed in a YouTube video posted by a user under the pseudonym "Maniacal Midget" on 1 February 2015, with the caption watch at your own peril. It consists of a HVY Docktug driver, who's on an unstoppable rampage through Los Santos, while seemingly possessed.
The video shows a white HVY Docktug truck driving out of Los Santos International Airport at night, which is rare in itself, as Docktugs are thought to never venture outside of the Airport or the Port of Los Santos. Confused, the player follows the Docktug for several miles. Along the way the Docktug smashes into traffic lights, drives increasingly aggressively and erratically, and even smashes into other cars. It is driving so erratically that it even manages to smash out one of its own headlights and indicator lights. The NPC does not seem to be possessed.
It becomes increasingly apparent that the driver appears to be coming under the influence of an unusual force. At some times he will be driving completely normally for some time, and then will suddenly switch into a possessed-like state, where his rampages cannot be stopped. Similarly, after a rampage, he may switch back into a normal state again without warning.
The Docktug seemingly cannot be stopped, despite all of the player's attempts. The Docktug is finally stopped at the very end of the video, when it is trapped on a slip road with nowhere to go. The driver of the Docktug then gets out and drags the player, playing as Franklin Clinton at the time, out of his Bravado Buffalo S. After a brief chase around the slip road, the Docktug driver suddenly switches back into his non-possessed state, as a normal NPC, gives up the fight, and returns to his Docktug. Here, the video ends.
The caption watch at your own peril is a warning, not a joke.