Complex sentence: He appears in the episode "Revenge of the Green Goblin" where Spider-Man first faced and defeated Green Goblin three years earlier, during which the opponents were unmasked to each other.
Split into simpler sentences: He appears in the episode "Revenge of the Green Goblin". In the episode's continuity, Spider-Man first faced and defeated Green Goblin three years earlier, during which the opponents were unmasked to each other.