Truck-kun is an Internet meme that refers to a common trope used in the isekai genre of anime, manga, and light novels, in which characters are transported to other worlds. Typically, the protagonists of the isekai anime or manga are sent to these worlds via reincarnation after death, and recently many isekai works have featured characters being transported upon being hit and killed by a truck. After several isekai works featured this as a means to kill their characters, a meme claiming the existence of a character named "Truck-kun" spread. It is purported Truck-kun's role is to kill people in their original world and subsequently send them to a new one. 

-from Wikipedia for those who don't know what the mothergrabbing hell Truck-kun is.