Joy to the World is the Christmas episode of House. It debuted on FOX on December 9, 2008.
A troubled sixteen-year-old, Natalie, is singing at her school's Christmas program when she suddenly becomes disoriented and vomits. She is brought to Princeton-Plainsboro Teaching Hospital, where the team discovers her liver is failing for an unknown reason. In House's office, they are exchanging Christmas gifts when House receives a mysterious gift wrapped in green wrapping paper. Kutner reads the note aloud, as it says "Greg- made me think of you." The present turns out to be Dr. Joseph Bell's Manual of The Operations of Surgery. House, annoyed, throws it in the trash. Afterwards, House conducts a differential diagnosis, with the team entertaining ideas such as alcohol abuse and pill-popping. None of the symptoms fit with the entire picture. When Chase and Kutner question Natalie's classmates, Chase gets angry enough with their cruel attitudes to let them know they're in serious trouble and they should act like human beings and tell him something that isn't bullshit; one of the popular girls says they slipped "magic mushrooms" into Natalie's food, and when she asks if Natalie will be OK Chase snaps at her that he has no way of knowing. Meanwhile, Foreman and Thirteen are still involved in the Huntington's drug trial. A woman whose disease is quite advanced drops out of the trial, saying that Foreman told her to "get over it" when her medication made her nauseous. Thirteen, annoyed, accuses Foreman of being like House.
After briefly suggesting the gift was from a former patient and old flame Irene Adler (a reference to Sherlock Holmes) Wilson tells the team that it is in fact last year's gift from Wilson himself, which House never opened. Wilson accuses House of needing to create the false illusion of a gift because he just cannot be nice to anyone. They end up betting that he cannot get thanked by a patient. Later, after Natalie's tox-screen was clean, Taub and Kutner find painkillers in her school locker, which makes them think she tried to kill herself. They later suspect tuberculosis, thinking she might have picked up something from the soup kitchen she normally attends.
To win the bet he made with Wilson, House puts on his lab coat (only the fourth time House is seen doing so, with the other occasions being the episodes "Mob Rules", "Sex Kills" and "Games") and acts very kind and caring toward his patients. A slightly dim woman, Whitney, who comes to the clinic with a terrible headache, compliments House on his hospitality, to which he responds, "If you can't be nice, why be a doctor?" He later deduces she is pregnant, much to her surprise. He then sarcastically insults her for not recognizing the common symptoms of early pregnancy, such as missing her period and putting on weight. She insists that she and her fiance are virgins, and asks for House to run a paternity test after he suggests that she has had an affair. He does run the test, but after sharing the results with them, he looks surprised, and leaves. He comes back later with the same set of results, and with a look of disbelief, states that Whitney is pregnant as a result of human parthenogenesis, a never-seen-before scientific phenomenon. Her baby only has maternal genes due to a spontaneous gene mutation which fertilized her egg, without ever needing male sperm. Her baby will be a virgin birth. Later, however, it is revealed that House faked those lab tests and just told them that story to cover up Whitney's blatant infidelity (as shown by the real results of the test), thereby 'saving' their potential marriage in House's eyes but saddling the fiance with a cheating potential future wife and someone else's baby (this is the "mistaking Good for Evil" that Cuddy refers to later in the episode but fails herself to rectify).
Things make a turn for the worse for Natalie, as she has a seizure, ruling out TB but bringing her brain into the differential, along with liver and lungs. Kutner suggests a mold allergy, to which the team goes to test her. Natalie admits to buying alcohol from her friend Simon, whom Kutner and Taub question. Taub suggests alcohol poisoning, but it turns out that she hardly even drank any of the alcohol she bought from Simon, as it was only a way to "look cool" and stay friends with him and he felt guilty over only associating with her in private because she wasn't popular. She goes into cardiac arrest, ruling out the alcohol theory. But her high blood alcohol level nonetheless suggests leukemia, and Wilson is brought in to help. While Cuddy desperately tries to rule leukemia out, Wilson discusses the likelihood of it and says that she will die, even if they kill all the cancer, due to her failing heart and liver. A double transplant would not even save her. Cuddy then has an epiphany after talking with House about the pregnant couple and gravely realizes the only other disease that explains everything: post-partum Eclampsia, which means that Natalie must have got pregnant and had a child. This turns out to be correct, and her friend Simon is the unknowing father. Natalie explains that she gave birth in an abandoned house but her daughter was stillborn. Cuddy searches the house and finds the baby girl, alive, being cared for by a pair of homeless squatters, and brings the baby back to the hospital where she reunites her with her mother. Unfortunately, due to the extent of Natalie's failing organs, she will die within hours (although this is not shown in the episode). The baby ends up being in good health but is kept for observation as she is premature.
In the end, the whole team is full of Christmas spirit. Kutner finds a former classmate he used to bully and apologizes to him. During the episode he is shown to be furious about Natalie being bullied and when asked says that he was never bullied. Cuddy plans to become a foster parent and adopt the baby, as neither grandparent wants to care for her as she will recall memories too painful for them to handle, with House wishing her "Merry Christmas, Cuddy." Thirteen tells Foreman that he is not like House, after he welcomed back the woman who dropped out of the trial and is taking better care of her. Foreman and Thirteen passionately kiss.
- Joy to the World at the House Wiki