Successfully complete "Knight's Passage" to unlock Lancelot, Gawain, and Percival as playable characters in Adventure mode.

Complete the indicated tasks to unlock the corresponding character in multi-player Battle mode.

Amy Rose: Defeat the final Boss.
Big the Cat: Find Big in every level.
Blaze: Defeat Lady Percival.
Jet: Earn a "5 star" rank on Great Megalith by getting a good time.
King Arthur: Collect all five of "King Arthur's Legends".
Knuckles: Defeat Sir Gawain.
Merlina: Defeat the Dark Queen in under one minute.
Shadow: Defeat Sir Lancelot.
Silver: Complete the "Lancelot Returns" mission in the Deep Woods.
Tails: Finish the first Castle Camelot mission.