Different Ending Poses
Normally after beating the game, Sonic will strike a jumping pose similar to the one he does at the end of Sonic 1 but if you collect all the rings during the ending sequence, he will either do his fist pump pose from Sonic 2 and 3 ending or turn into Super Sonic if you also have all emeralds.
Sneak-Peak for Episode 2
Beat the game with all 7 Chaos Emeralds. You'll get a sneak peak at something that will be in Episode 2.
The sequel to the award winning Hellblade: Senua’s Sacrifice, Senua returns in a brutal journey of survival through the myth and torment of Viking Iceland. Intent on saving those who have fallen victim to the horrors of tyranny, Senua faces a battle of overcoming the darkness within and without.