Shailene Woodley and Ansel Elgort may be leading The Fault in Our Stars, but supporting the love story of Hazel Grace Lancaster and Augustus Waters and constantly cutting their tear-jerking tension with hilarious one-liners is fellow terminally-ill teen Isaac, played by Nat Wolff. The 19-year-old actor tells The Hollywood Reporter of Isaac, the one-eyed, lovestruck best friend of Augustus who loses his sight completely in the film. “This is probably the hardest character I’ve played because it seems so simple.”