You see, all this "common enemy" talk gave him an off-camera Epiphany Face. He heads for Cyrus's room and he figured out that there's a common enemy in Cyrus's body that caused all of his problems: a teratoma. What is a teratoma? House describes it as a "congenital growth which can be filled with almost any kind of tissue." I call it "one of those horrible tumors with hair and teeth. Yes, HAIR AND TEETH! THERE COULD BE A TUMOR IN YOUR BODY RIGHT NOW GROWING HAIR AND TEETH! SOMETIMES THEY CAN GROW LITTLE ARMS AAAHHHHHH THE HUMAN BODY IS A NIGHTMARE!" Anyway, Cyrus's teratoma was not full of hair or teeth or little arms, but with cells that differentiated into brain cells. Those cells somehow left the teratoma and entered Cyrus's blood stream, where his immune system saw them as a foreign object and created antibodies to fight them. Unfortunately, those antibodies started fighting the brain cells in Cyrus's brain, too. And then, somehow, some of the undifferentiated cells in Cyrus's teratoma also leaked out and started turning into all kinds of random specialized cells, causing his organs to fail. And also created those tumors and made them grow rapidly and were full of cancer too, somehow. Um, I'm not really sure how that all worked out in the end. I watched this several times and I still couldn't figure it out. I have a feeling the writers couldn't, either. Also, even though you'd think the teratoma damage was already done now that the cells have leaked out and created havoc all over Cyrus's body, House says that all they have to do is cut out the teratoma and his cancer tumors and he'll be just fine. That's not good enough for Cyrus, of course, who is still too upset about Jennifer to be happy about living.
That night, a blonde woman rolls over in bed next to Chase, who clearly isn't as chaste as he claimed to be, not like anyone cares. Also, is that blonde woman the same woman who claimed to be Jennifer? Or is that the PPTH nurse Foreman paid off? Or someone else entirely? I honestly can't tell. White people all look alike. Foreman monitors his own blood pressure in a dark room. Fun. A third Jennifer Williams shows up in Cyrus's room. This time, it's the real one. Hadley watches them from the nurse's station as House walks up and offers her a potato chip. She says this Jennifer Williams has the correct birthmark and Cyrus is renting her an apartment. House predicts that this will end horribly. Hadley says it probably will, but even if Jennifer Williams takes Cyrus for a ride and he ends up with nothing, she thinks he'll always be hopeful and therefore, always be happy. House decides that Hadley is trying to convince herself that she was meant to be miserable even before almost everyone in her family got Huntington's because she can't deal with hating the universe for making her life so horrible. "Fatalism is your survival mechanism," he says. Hadley asks what House's excuse is, then, since his life sucks, too. Yeah, but not nearly as much as hers does. "We are who we are. Lotteries are stupid," she repeats. Totally. That's why if you want money, you should just sue your daughter's hospital for it. Or let a co-worker pay you $100 to flirt with another co-worker. Those things aren't stupid at all.