Gregory House made a bet with James Wilson that he could get a patient to give him a Christmas present as all that was required was to act nice to them. As part of his plan, he put on a lab coat, went to do clinic duty and put on his best bedside manner.
Whitney was his first patient. He saw on her chart and intake form that she had been gaining weight, that she had a craving for salt, and was reporting nausea every morning. He walked in and politely introduced himself and asked what he could do for her, while noticing that she was wearing a motion sickness patch appeared to be wearing a top that was a size too small. He immediately surmised she was pregnant and started talking to her about her problems, figuring she was seeking pre-natal care. Instead, when he told her that her symptoms were normal for someone who was pregnant, she expressed surprise and said she didn't know. Dr. House immediately lost his composure and noted that it was obvious to him and it should have been obvious to her - hadn't she missed a few menstrual cycles? She protested she couldn't be pregnant as she had never had intercourse, but Dr. House just went to get a urine sample cup so he could confirm. She insisted she must have gotten pregnant by fooling around with her fiance. Dr. House said that was possible, but in her case, it was because she slept with someone else.
Later, Whitney came back with her fiance to get Dr. House to repeat that it was possible to get pregnant without intercourse, Dr. House confirmed he said that, but it was clearly out of context. He tried to ignore them, but Whitney kept imploring him to tell her fiance that the child must be his. However, the fiance insisted he was a virgin and he demanded a paternity test. Dr. House said it was too dangerous at this stage of the pregnancy, but when Whitney asked if that was true, he had to admit it wasn't and he was just trying to delay the inevitable. He agreed to run the test.
When Dr. House met with Whitney and her fiance again, he looked at the results and looked very surprised. He left. When he came back a few hours later, he told them he had to run the test several times to be sure, but that their child appeared to be the first human case of parthenogenesis - a spontaneous spliting of the egg cell without fertilizaton with a sperm. The fetus had exactly the same DNA as the mother. Whitney and her fiance were astounded. Dr. House wished them a Merry Christmas.
Later, Dr. House received a beautifully wrapped present from Whitney. Without even opening it, he took it to Wilson's office and threw it on his desk in triumph.
However, Lisa Cuddy caught on. The DNA testing machine was broken and all the paternity tests were being sent to an outside laboratory. There was no way House could have checked the results in just a few hours. She realized he faked it and House admitted to doing it to restore the fiance's confidence in Whitney.