Ninja Boy

I'm going to tell you a secret. Please don't spread it around - a superhero's secret identity could be at stake.
Are you ready? Here it is... Jake is a Ninja Boy. There's something special in his blood.
I first learned about this special component in my son's blood at his last doctor appointment. See, the doctor wanted to do a blood test. Jake, of course, flipped out. Nobody was surprised. This is the same boy who brought us the famous flu shot incident, after all. The doctor left the room so that I could "help him calm down." And then Jake shared with me his secret...
The Ninja Boys (Jake and two of his Kindergator buddies) have something special in their blood! It's what makes them Ninja Boys, you know! He just could not let the doctor test his blood. It would compromise his secret identity!
I totally understood. But I had to explain to my sweet (and very serious) Ninja Boy that his health had to be our first priority. Without his health, how would he be able to perform his Ninja Boy duties? Maybe we'd have to trust the doctor...
Well, Jake wasn't convinced. He decided that he'd just have to explain to the doctor that his blood was special and could not be tested. When the doctor returned, he was met by a calm(er) Jake, who explained, "There's something you need to know. My blood has something special in it."
The doctor was convinced! (Okay, so he had decided before returning that having the screaming child pee in a cup would be sufficient, but the Ninja Boy doesn't need to know that.) We were able to get out of there without giving up the secret. Apparently, Ninja Boy DNA doesn't show up in a urine sample.