Darrin is doting on Samantha upon news that she's pregnant. Samantha is less concerned about what she believes is Darrin's overboard behavior than about what Endora will think about becoming a grandmother. Endora isn't nearly as abhorrent to the news as Samantha thought she would be, but is surprised by what she hears is Darrin's doting. However, by the time that Darrin returns home from work, Endora doesn't see that doting as Larry has convinced him that it is healthy for Samantha to continue to do hard work. As Darrin states that he will still go through every pregnancy pain along with Samantha, Endora, without either Darrin or Samantha's knowledge, decides to teach him a lesson by making it a reality, including him feeling every hormone induced emotion associated with pregnancy. Darrin doesn't know why he is feeling as bad or emotional as he does, so when he goes to the doctor for a check-up, he is surprised by the doctor's assessment that it's almost like he's pregnant. Darrin rightly assesses that Endora has placed a spell on him. Samantha has to try to convince him that he really isn't pregnant, and that he will thus not become the world's first man to give birth. Convincing him will not be an easy task.
—Huggo