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" in the most recent episodes 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.
On June 12th, 2013, Lyle revealed on Tumblr that he has decided to go by Lyle Lettau rather than O'Donohoe in honor of his grandmother, and that he would be credited as such in the 13th season of Degrassi and onwards.
He is a huge fan of Lana Del Rey, and frequently quotes her songs on Twitter and Tumblr.