Yes Classic Sub has a fairly well documented infinite, I'm not sure if that is it. Its not something I've gotten, just heard about a lot. The robot ninjas are one of the best characters to get it on, they are more open to it. Also, Jax and sheeva are good to get it on. From what I know it has been done on all the characters except the female ninjas.

Just remember that even a legitimate infinite can be done wrong and be blockable. If you are just practicing on an empty P2 or against the computer it won't be blocked in the middle and the # of hits and Damage can all add into the final display. But, just because it adds to the counter doesn't mean it can't be blocked in the middle. So if you want to see if its really an infinite get someone to hold block on the P2 side after the first hit of the combo, just to make sure it is unblockable all the way through.