In Akumajou Dracula X: Rondo for Blood for the PC Engine, there's a hidden staircase right before you fight the final boss. Once you walk up the steps to Dracula's chamber, you just have to jump around, hold up, and eventually you'll latch onto the invisible steps, carrying you to a secret room filled with cash. I've known about this for years and years, but what I didn't know was that this is actually a reference to a glitch from the Famicom Disk System version of Akumajou Dracula, the first Castlevania game.