Young Man Rivers is the grandson of Old Man Rivers. He made his debut in the Foster's Home for Imaginary Friends Season 4 episode "Neighbor Pains". He makes funny faces at his enemies Mac and Bloo. He is the arch nemesis of them too. His only speaking appearance was when Bloo made faces at him while he's playing blocks. He made two more appearances in "Say It Isn't Sew" and "Goodbye to Bloo".