The title is not a joke. Without this information, the full game is impossible to access past level 16. In level 16 itself, (The beach resort level, just after the surfing section) your goal is to reach the resort bathroom and "drain the dragon". The exit door next to the resort counter is locked until you do. However, Even after you go to the toilet and empty your bladder, the exit door will still be locked, telling you that you still have to piss. The solution to this is painfully simple. Back in the bathroom, right in front of the toilet, there is a white octogon on the floor. Go to it, crouch, and press E, or whatever your "use" key is. If done correctly, there should be about a tenth of a second of lag. Go back to the exit door, and use it. It'll literally just say "okay" and after a few seconds, open up and let you out of the level.

Side Note: As far as I know, I was the first person to discover the solution to this bug, and it took me actual years to figure out something so damn simple. I mean, nobody out there makes guides for this game, or even really plays it much so I'm kinda all we got. I wonder if I've played the most Grezzo Due out of anyone in the entire world. Hm.