Gareth Grimes is a character that appeared in Diary of a Wimpy Kid: Old School. He is one of Greg's cabinmates that stayed at Hardscrabble Farms for a week.
Gareth Grimes is the boy that collapsed and smash into Rowley during the trust fall activity because a boy named Jeffrey Swanson had bang into them and one of his teeth was missing, then everyone got down their hands and knees to look for his missing teeth until his cabinmate named Emilio Mendoza found it on Rowley's forehead which was stuck in it. Then Mr. Jefferson told Emilio to get the nurse to help and she brought the damp cloth to stop the bleeding from Gareth's front tooth dislodged. But the nurse cannot take out his tooth from Rowley's forehead because it was still lodged. His father called his wife, Mrs. Jefferson to come pick him up to get checked out. Greg wondered, he don't know if she sent him to a doctor or dentist, because he has no idea what he do for that sort of thing. On Friday morning, Rowley returned to camp with a bandage on his forehead, possibly after surgery. Due to the infection from Gareth's tooth that stuck on his forehead which infected him and he was gone long, from Tuesday to Thursday, possibly he stayed at home or at the hospital. He brought the tooth and give it back to Gareth, but Greg wondered that he was not sure what he was supposed to do with his tooth at this point.
- Diary of a Wimpy Kid: Old School (First and only appearance)