The Mechanic was a proven myth in Grand Theft Auto Online.
The mechanic was a supporting character in GTA Online, until an update eventually removed him due to his incompetence. He was employed by the player as a personal mechanic, who would deliver the player's vehicle to them whenever requested.
Many players had reported the Mechanic as behaving quite strangely. Even though the mechanic was employed by the player, he would act hostile towards the player if he was attacked, or physically provoked. It is unknown if this was the result of an AI glitch, or if it was intentional, but this strange observation has been discussed thoroughly in online forums. It was unknown why the mechanic behaved that way.
If the player called the Mechanic to deliver a car for them, the mechanic would have driven to the player's location, but kept on driving, not bothering to stop for the player. If the player attempted to retrieve his car, the mechanic would act in a very aggressive way towards the player if provoked, and attacked the player by any means necessary. It is even said that he could find a gun to shoot any attackers. Once the mechanic had stolen a vehicle, he would have driven all around the map until being caught by the player, but in some circumstances, committing suicide by jumping out of the vehicle or driving into the water.
The mechanic in his own nature was quite a strong NPC and he would sometimes even prove to be impossible to kill. The easiest way to kill him was via headshot, but sometimes this was ineffective. It was said that the mechanic can disappear at will as well. If the player tried to run over the mechanic, or kill him with an explosive, he disappeared.
The only explanation for the Mechanic's erratic behavior could be that his AI encounters a glitch, possibly due to overloaded servers, or a slow internet connection. Any of these factors can somehow affect the Mechanic's AI, causing him to break from the script when delivering the player's car, so he may keep on driving.
Valentine's Day Massacre Update
With the Valentine's Day Massacre Update for GTA Online, the Mechanic was removed from the game. Due to the Mechanic's tendency to crash players' vehicles into walls, or scratching them while bringing them to the player, the Mechanic became more of a burden. When a car is requested from the player's garage, it will instead spawn outside of the player's line of sight on a nearby street or similar. The only remaining presence of the Mechanic is in phone calls with the player.