Shortly thereafter, Ted's brother Hal (who insists Ted is his brother, and not the other way around), enters the studio looking for Ted. Hal and Ted have not seen one another in five years. Hal takes an immediate interest in Mary, especially after she recognizes him from commercials and other advertising that he's done. Meanwhile, Ted walks in and becomes instantly flustered upon sight of his brother. He goes into Lou's office and asks Lou to offer him a (fake) raise in front of Hal, just so that Hal thinks he's that good. When he comes out again, the two brothers discuss going to dinner together, and Hal suggests that they take a date, thinking that Mary might accompany him. Ted says that Mary is his girlfriend, and pleads silently with his eyes for Mary to go along with the act. Mary goes along with it out of kindness to Ted, and agrees to introduce Hal to Rhoda, per Ted's awkwardly phrased suggestion of it.
Mary preps Rhoda for her pompous date, and says how she's never seen two siblings so competitive. When the guys arrive, they end up arm wrestling at the dining room table, until Rhoda puts a stop to it by announcing that the winner gets to pay for dinner. Ted says their behavior is a result of their parents' encouragement of competition when they were kids.
At the fancy French restaurant where the four dine, Ted makes his usual gaffes when it comes to etiquette, calling the garcon "stingy" when he pours the swallow of wine for Ted to sample, and chugging his glass before they toast. Hal comments on the fact that for a couple in love, Mary and Ted are more like kids on their first date. Much to Mary's chagrin, Ted overcompensates and puts his arm around her and even threatens to kiss her to prove that they really are a couple.
When the four return to Mary's, Hal goes upstairs with Rhoda to look through her magazine stash for ads of himself. Ted insists that he stay at Mary's to make it appear as though he really is her boyfriend. He won't leave, and they stay up all night and play "Go Fish" and other card games. Finally, dawn is breaking and Mary is so punchy she can hardly think, and is begging Ted to leave. The phone rings and it's Rhoda. Apparently, Hal left a half hour after they got back from dinner, taking a cab back to his hotel. Mary wants to scream.
That afternoon at the office, Mary is so tired that she makes coffee and forgets to add the beans. Ted comes in, perfectly refreshed because he slept in until after noon. He wants Mary to go out with them again, but Mary refuses. In her fatigue, she says something almost unintelligible about Ted outdoing his brother by being the first not to try to outdo him. It makes sense to Ted, and when Hal wanders in, Ted explains to him that Mary is not his girlfriend after all, and that it was an act to impress him. He further explains that he normally wears glasses (and puts them on), and goes on to tell Hal several other shortcomings. Mary is delighted and in disbelief. Hal is also taken aback, but when he recovers he tells Ted that his work has been on the decline for years, and that he had to pay seven hundred dollars for his left dimple, which was not there when they were kids. Mary can't believe that now the two are competing over who is the humbler! The brothers decide that they have a lot to discuss, and agree to go out to dinner alone together that night.
Back at Mary's apartment later that evening, Mary and Rhoda agree that Hal was way too pretty to date, and that they'd never seen so many heads turn the night before, and all on account of Hal.