One glitch I've pulled off thanks to a user on Youtube is the "Invincible Spyro" glitch for the first game.
To pull it off, go into Stone Hill. Once you are in Stone Hill, deliberately let yourself get damaged until you have only one hit point left. That means no Sparx. This is important. After that, run towards the exit. There should be a dragon statue here if you just started a game. I don't know if it'll work if you already freed the dragon.
Anyway to continue, get the ram enemy to chase you. You want to position yourself just right so that when you are hit, you are knocked back into the statue and activate it. If you die, keep trying and experiment until you can successfully get the ram to launch you into the statue to activate it. If you did it right and activate the statue, you will see a cutscene of the freed dragon. When it's over, will Spyro just die right there since he was hit one final time?
Nope. He's alive. Return back to the Artisans world and you will notice a couple other side effects. Spyro is now invincible. He can touch enemies without taking damage. He can jump into the deadly water without dying. This seems like it could be fun and help you advance through the game without dying once, right? Nope. Turns out this glitch is more of a curse than a blessing.
First off, if you jump in the water, you'll stay stuck there. Forever. No jumping, no dying, you're stuck there. You also cannot even leave to go anywhere. All the portals are now inactive functionally. While you can see them just fine and they seem normal, if you try to pass them, you'll be blocked as if it was a solid surface.
You might think to yourself "well I'll just get Sparx back and things will go back to normal" but you couldn't be more wrong. Sparx will not appear again. You can try all you want to, he is not coming back. You're stuck in Artisans forever, eventually running out of enemies and having nothing left to do except run around in circles, flaming sheep.
Why doesn't Sparx reappear? I have a theory. Sparx is set to change color when Spyro takes damage. To me, this means his sprite is in tune to Spyro's sprite's health meter. When Spyro sets an animal on fire, if Sparx is already there, if Spryo has any damage done to himself, Sparx will eat the butterfly that emerges from the animal. This fully supports the idea that his sprite is in tune to Spyro's health. When Spyro has only one hit left, Sparx immediately emerges when he flames an animal.
When Spyro becomes invincible, his health meter is scewed and it's impossible now for the Sparx sprite to know when to appear or not. It is likely that, because Spyro is invincible, the health meter is mistakenly seen as full, and thus Sparx will not appear. To the Sparx sprite, the Spyro sprite has a full health meter and doesn't need assistance. This is just my theory though.
The only thing you can do is either kill yourself through a glitch in the water, which, if executed right, will cause Spyro to fall through and die falling, or reboot the game.
