Season 5, Episode 4: "Baby Shower"
Just as "The Job" delivered the long-awaited turning point in Jim and Pam's relationship, "Baby Shower" gives us Michael and Holly making it first-date official. After finding out about Jan's pregnancy via sperm donor, Michael is still determined to treat this baby like his own, or, as Jim so aptly put it, "This baby will be related to Michael through . . . delusion." Of course, that means throwing a baby shower in the office, but — plot twist — Jan shows up having already given birth. Never one to be discouraged, Michael forges on with the shower, as well as with his plan to prove he is completely disinterested in Holly to avoid hurting Jan's feelings. After Jan flat-out tells Michael to not date Holly, without any explanation, he proves that he does in fact always remain true to his feelings, and so we get the start of our happy ending.