He heard a sound next to him, the taps being turned on again? The same tomfoolery as before, switching on the appliances in an effort to play mind games. Not this time! Because the Prince was invisible, he simply closed his eyes and relied entirely upon his hearing. No matter how silently a person attempted to move, they would still make a noise whenever their feet landed on the ground. In fact, if you knew what you were listening for and focused only on a gentle footstep, you could, in theory…

"Got you!" he yelled, grabbing hold of the Prince's collar and slamming up against the fridge. He got into the Prince's face, breathing heavily and deeply chuckling. "You know, that was a fancy trick you just pulled! How did you do it? And just to warn you that if I think you're lying, I'll stick my knife somewhere non-fatal and give it a nice twist."

-Lulu's Bizarre Rebellion Chapter 29