Things definitely wrapped up on last night’s mid-season finale of Mad Men. Some stories came to a close—like Bert Cooper’s and Don’s and Megan’s relationship—and others were close calls. To wit: Ted’s plane ride scare and, last but not least, Don’s will-it-actually-ever-happen departure from the agency.

Even though there were drama-filled moments in last night’s episode, the show closed out with an extremely unexpected song and dance. Read: Cooper’s final moments on the show were dream-like and musical-esque. He sang a song to Don reminding him that the best things in life are free.

And there was an epic event that brought all the characters together—Neil Armstrong landing on the moon. But the real triumph came when Peggy delivered a killer commercial pitch to the Burger Chef client. She had everyone eating out of the palm of her hands.

For that memorable moment, Mad Men costume designer Janie Bryant dressed Peggy in a blue-and-green striped dress. “That costume was really important because she needed to wear something that was really impactful,” Bryant exclusively tells us. “I felt like that costume said, ‘I am a serious advertising woman. Take me serious,'” she adds.

For more from Bryant on last night’s looks (and other memorable outfits from season 7), browse through the gallery.