I give up. First time, I ran around in my suit and turned on the lights and talked to both characters. Nothing.
Second time, I ran around naked, turned on all the lights, talked to all the coupling couples, got the gun, killed all enemies, talked to the guy who told me to put on my suit, so I put it on, and, uh, nothing again.
I'm sure I visited all of the rooms. Is the room with the penis-creatures somehow significant to get the ending?
Or, in other words: What are you supposed to do? :/
Still foolishly waiting for the third Mondo game <3