Garrett is Bryce's friend, and helps him throughout the book/movie.
Garrett first appears, talking to Bryce about The Three Stooges, saying there's Moe, Larry, and Joe. Bryce and Garrett both notice Juli in the sycamore tree, protesting against cutting it down. The bus appears, leaving Bryce and Garrett with no choice, but to get on.
He appears later with Bryce who asked him what is a difference between a rooster and a hen. He answers, saying "Well, a rooster's big, with longer feathers and got that rubbery red stuff growing on there heads, and around their necks too.". They then peek into Juli's yard, looking for a rooster. They find a large coop, full of chickens. Garrett throws, what it looks like a book, at the coop, alerting the chickens to come out. When Juli comes out to feed them, more chickens come out. Then Garrett says, "There all chickens.". The sentence repeats, said by Bryce to his father, as the scene switches to Bryce eating dinner.