Because it makes little boys want to test their parent's limits. It should really be renamed "Calvinerone" since it causes Calvin-like behavior. We are actually considering changing Quarto's name to Calvin. Let me explain.
Frodo had gone to the store to buy us an air mattress. When he came home, it was time for the boys to go to bed, so he got Quarto settled on the kid potty. He quickly realized that Quarto was going to be awhile, so he went upstairs to begin dismantling our bed and setting up the air mattress. During these activities, I was in the midst of temperature taking, dish washing, kitchen disinfecting and other "flu-survival" activities with the girls, so I wasn't aware that Quarto was still sitting on the potty until Frodo called down (about 10 minutes into Quarto's potty time) and asked me to check and see if Quarto was done.
I popped my head into the bathroom and asked, "Quarto, are you done?" "Not yet," he replied, casually. I told him that I would be back in two minutes to get him dressed and brush his teeth. As I turned to leave, Quarto said, "Look what I do, Mom." I look, expecting to see a toy car he has brought with him or a boat or other tub toy that he often plays with while he sits on the potty. It was a tub toy that I saw, but I was quickly snapped out of my casual attitude.
Quarto was sitting on his potty... peeing into the tiny little opening on a fish-shaped water gun then shooting urine around the bathroom. "Look! I go far!" Quarto boasts of his shooting ability. I leave the bathroom immediately since my first instinct is to begin laughing hysterically and inform him that, being a boy, he could do-away with the plastic, fish-shaped "middle-man". I decide that walking away and calling Frodo to observe his youngest son's ingenuity would be more mature.
Frodo looks, rolls his eyes, sighs something that sounds like "Calvin", and goes back to setting up the mattress. I attempt to sound serious (i.e. control my snickering) while lecturing our three-year-old about why we don't shoot pee out of water guns then have him help me clean up the mess... what I can find of it. It still smells a little like a latrine in there. Sigh.
How do they come up with this stuff? It's gotta be the Calvinerone.