Knuck Knuck! Who's Here? Sonic Boom : Season 2 Episode 12

During a fight against Eggman, Knuckles suffers amnesia. His friends try to help, reminding him of his worst blunders via flashbacks. But he becomes more depressed when he learns that he is the last of his kind - the final echidna. Feeling all alone in the world, Knuckles sets out to find a foster family among the Villagers who might be willing to take him in.