Sonic Underground (1999)

S1E12 A Hedgehog's Home Is Her Castle

The Hedgehogs get a message they think is from their cousin, stating that a castle has been bequeathed to Sonia. Excited by the prospect of turning it into an Underground headquarters, Sonia can't contain her joy. However, when Sonic, Manic, and Sonia reach the castle, they find it to be an old, crumbling building shrouded in darkness. Inside, each Hedgehog encounters a mysterious figure that bears a striking resemblance to their mother, leading to unexpected and emotional meetings.