Lyle Lettau (born O'Donohoe) is a Canadian actor, best known for portraying Tristan Milligan, being introduced in the second part of Season 11 of Degrassi. He is known for portraying, "The Brain" from season 12 to season 15 of the TV show, Arthur. He is currently a senior at Flesherton's Grey Highlands Secondary School. His inspirations are Marilyn Monroe, Andy Warhol, and Lady Gaga. 2015 Won Joey Award as Best Actor in a TV Drama Leading Role 16-19 Years