Wasn't that secret video unlockable in Deception? It was titled, "Mythologies Bloopers," or something.

I know what you're talking about, it's only available on the PS version (I did it on the N64, but didn't get the video); to view it, beat Shinnok's demon form by using the Polar Blast and recharging your Ice Meter with an Urn of Vitality, and repeating the process until he falls off the bridge. Just remember that the closer he gets to you, the sooner he'll slaughter you, so you'll have to distance yourself after each blast a little bit before recharging and attacking again. Just don't go into the portal until he is defeated.
The thing is that the game does not have enough Urns to recharge you enough to allow you to do this properly, so you have to use this password. NXCVSZ gives you 10 Urns to start the game with, and you need 7 of these to ensure you can beat Shinnok (the game has only 6 to be found).
The video that reptile88 posted is the video that is shown, and is also viewable if you have MK:D. Hope that helps you out!