Alternate ending
Successfully complete the game with all 40 Dark Gems, 100 Light Gems, and 80 Dragon Eggs to view an alternate ending.
Defeating Red -- Robot version
Dodge all of his attacks, including his mines, laser eyes, and jet flames. Eventually he will turn to normal and stand still. Then, some rockets will appear. Light them with your flame breath. It will hurt Red. The whole thing starts over again. Use the same tactics. After that, dodge his attacks again and some gadgets will appear. Light them with your electric breath. It will hurt Red. Keep dodging his attacks and lighting the gadgets with your electric breath. You will eventually defeat him.
Secrets
Collect the indicated number of Dragon Eggs to unlock the corresponding option in the "Secrets" menu:
Concept Art: 1
Character Viewer: At least 11.
Ember Model: At least 21.
Flame Model: At least 31.
Sgt. Byrd Mini-Game: At least 41.
Spyro Turret Mini-Game: At least 51.
Sparx Shooter Mini-Game: At least 61.
Blink Mini-Game: At least 71.