If you use Key Input Processing, you could make it that the person needs to push arrow keys in certain directions. You could have pictures showing the directions, but that's a very complicated technique for the newcomer.
If the Enter Hero Name function works, you could have the player be asked to name a random character with no sprite whatsoever, and no current name. Then you could have Conditional Branch check if Hero's Name is the same as the password, and have a series of stuff happen if it's right. This series of events works in both RMXP and Rm2k3, granted the Enter Hero Name works.
Need more detailed?