Matthew Weiner spent most of Memorial Day in his office writing the final finale of “Mad Men,” while fans parsed the state of the Sterling Cooper universe after Sunday’s midseason finale.

He took a few moments away from focusing on next year’s last seven episodes to discuss some of the broader themes and plot points from this year’s first half of the farewell season.

SPOILER ALERT: Stop reading if you haven’t seen “Mad Men” episode 7, “Waterloo.”

Although the seven episodes seemed to be over in a blink of an eye, Weiner said he and his writing team “really tried to tell a whole season’s worth of story.” Now that “Waterloo” has aired, the truth can be told. The writing team had long planned for Bert Cooper to die while watching the July 1969 moon landing. And they’ve been wanting to script a song-and-dance number for the character played by Broadway vet Robert Morse since the beginning of the show, but felt it was important for Morse to not break character too soon.

Weiner confirms that the focus on the mending of the relationship between Don and Peggy was crucial to allowing both characters to grow this season. And yes, Joan seems inordinately bitter toward Don, but not without reason.

Variety: What were the most important character development points in these first seven episodes of the final season?

Matthew Weiner: Within the language of the show this season started with Don and Peggy as far away as possible from each other. Don was screwing everything up. He was sort of stuck in limbo about the job and everything that had worked for him in the past. We wanted to do a story about a guy fighting his way back up in the company. Don wanted to change but in this situation whether you want to change is one thing, whether other people can accept that change is another. There are a lot of people who can’t believe things will possibly work out and how Don can end up doing the right thing and taking pleasure in the work.

When did you decide to give us that showstopper of an ending with Bert Cooper’s song and dance number on “The Best Things in Life Are Free”?

Weiner: The ending is deeply rooted in the language of the the show. We’ve always had flashbacks and we’ve tried to take advantage of offering a filmic experience with POV. Remember at the end of (season one closer) ‘Carousel’ Don goes back to his empty house and has a very deep fantasy that his family is still there. After Roger (in ‘Waterloo’) says that the last things he said to Bert were “the words to some old song,” we wanted to use that to have Don give himself a message that there were bigger things in life than success and money.

How long have you been planning Bert’s death?

Weiner: The plan from the beginning of the season was that Bert would die during the moon landing and come back and sing that song. I heard it on an old-time radio show. It’s a song from the Great Depression — you couldn’t get anything more on the nose. I love what it says … Obviously we wanted to take advantage at some point of who Bobby Morse is. We’ve been thinking about it for the entire run of the show. For about 15 years, you could not pick up a paper and not see something about Morse doing something on stage. He was really part of Camelot, personally and artistically. We wanted him to break character for a second in Don’s imagination and give him a message about life and death.

Were you nervous about the reaction to the sequence?

Weiner: It was a lot of work to pull it off in our (production) space and not make it campy. It had some sentimentality to it. It’s for anyone who has an imagination or is lucky to have had the experience of seeing someone who wasn’t there. The message from Bert to Don is that life and death are bigger than money.

What were some of the highlights for you this season?

Weiner: The most emotional thing in the whole season to me was seeing Peggy and Don working together again finally (on Burger Chef) and when they said “We got it.” When you see their mentor relationship come back to life. And then later (in “Waterloo”) when the partners meeting (about the McCann-Erickson buyout) is over and Don tells Peggy “I’m going back to work.” He knows that she got Burger Chef all by herself. It’s exciting to push somebody on a bike and then let go.

He seems gratified by being able to help her — especially given what’s gone on in his love life?

Weiner: You can’t give somebody confidence — then it’s not their confidence. Peggy thought she was a boss before but being the boss is riding to the occassion. Don realized that for him to pitch (Burger Chef) was of no use to her. I don’t know if it was a sacrifice on his part but it was certainly a chance to come through. And part of (Don’s success) was that she came through it in her own way. She did not do the pitch as Don would have. It’s very satisfying to see people achieve under high stakes. Don trusts her and she delivers.

You seemed to be commenting a lot about the nature of television and shared viewing experiences by wrapping this thread around the moon landing?

Weiner: The irony is the fact that she’s pitching a commercial about turning off the TV just as we’ve come through probably the greatest TV moment we’ve ever had.

Why is Joan so angry toward Don? She seems inordinately bitter towards him.

Weiner: Do you have any friends who cost you $1 million? Joan slept with the guy from Jaguar, and then Don impulsively fired Jaguar just as the company was going to go public. So she did all that for nothing. Then they had to merge with (Cutler, Gleason and Chaough). To have some lone wolf fueled by alcohol is not good for a company. Don really did cost her almost the same amount of money she ended up getting from the (McCann-Erickson) buyout. Christina Hendricks is such a good actress that you can see Joan is overwhelmed by her new wealth as she walks out into the bigger office from the partners’ meeting. The audience forgives Don because we like Don, but if you try to see it from Joan’s point of view you can understand it. Peggy was the same way. Don essentially forced her to come back to her old agency (by orchestrating the merger with Cutler Gleason), he ruined her relationship with her boyfriend, humiliated her in front of clients and then sent her boyfriend away to California.

By the end of this mini season, the core characters seem mostly contented, compared to past finales.

Weiner: Hopefully there’s some bittersweetness to this, considering that they have sold the company.

Give us the tiniest glimpse into next season.

Weiner: I can’t … I can say that it’s almost finished. I have said from the beginning that a lot of this season is about the material and the immaterial. So many of their concrete needs have been met, so now you ask yourself, what’s left?