[phoenixwright7]

If it's the Master Emerald making Super Sonic vulnerable to Knuckles' punch, then wouldn't he have been vulnerable throughout the entirety of the game? I mean, outside of the last boss, I can't think of a single instance where Super Sonic was as vulnerable to damage as he was during the first cut scene...

Don't know if this counts, but if you use debug mode to go through knuckles' path in Ice Cap Zone, the ice spikes does damage Super Sonic!

Ah... Forgot about that... Question, do they damage Super Knuckles? If not, then I don't think it really counts.

[DigitalDuck]

Don't know if this counts, but if you use debug mode to go through knuckles' path in Ice Cap Zone, the ice spikes does damage Super Sonic!

Pffft. You don't need debug for that.

Anyway, that's a bug, semi-fixed in S3K: hitting it while super/hyper destroys it without harming you, but it can still hurt you during temporary invulnerability.