Sonic Boom (2014)

S2E12 Knuck Knuck! Who's Here?

In the midst of battling Eggman, Knuckles experiences a sudden loss of memory. His companions attempt to jog his recollection by showcasing his past mistakes through vivid flashbacks. However, the situation worsens when Knuckles discovers he is the sole survivor of his species, the last echidna. Overwhelmed by loneliness, he embarks on a quest to find a new family among the Villagers, hoping to find someone who will accept him and fill the void in his heart.