Exclusive to the PS1 version is a secret battle with the Reaper. To reach him, all you have to do is reach the end of Stage five without using a continue. If done right, instead of going to Stage 6, you'll be transported to an alternate dimension where you will be asked three questions.

You need to answer the following way:

1) No, why?
2) Of course not!
3) Yes, I do!.

If you answer anything else, you'll be kicked out. If you answer correctly, you'll fight Reaper. The game continues normally after that.