Uncle is one of the main characters in the game and one of the most important, as he gives tutorials on how to play the game. At times Uncle can be extremely annoying leading to car crashes, and his dialogue can not be deactivated.
As of the Hungary Update, Uncle no longer joins you on your journey, and exits the car to stand by the garage after the tutorial is completed. His removal from the journey is due to his often very buggy behavior. The developers of Jalopy have stated that he will probably be re-added some time in the future.
Although he was supposed to have been removed, Uncle would still occasionally tell the player to "put that back" if a part was removed from the engine, and some reported him appearing in the car during the journey. These bugs were fixed in patches following the Hungary update.