Mad Men is more than a show about a 1960s ad agency. It’s a show about complex connections between complex characters - none more so than Don Draper and Peggy Oleson. Theirs is the definitive relationship of the series - the one that drives the show.

The connection between Don and Peggy is not easily defined. It started innocently as an employer and his secretary but, through the various twists and turns that played out over seven seasons, the best way to describe the duo is simply to call them best friends. Here are Don & Peggy’s 10 best moments.

DON MEETS PEGGY

Peggy is hired to be Don’s secretary in the pilot episode. Their first encounter comes when Peggy wakes Don from a nap. “Who are you,” he asks, to which she nervously replies “I’m Peggy Oleson, the new girl.”

Peggy informs Don that Pete Campbell is waiting outside. Don asks Peggy to briefly entertain him while he composes himself to which she stoically responds, “Do I have to?” Don, obviously not used to push back from his secretaries, flashes a half-smile and the rest is history.

PEGGY CALLS DON A MONSTER

Being an ad man in a dog eat dog world has given Don somewhat of a thick skin. He is an unfaithful husband and living a lie but still goes through most days with a smile. But when Peggy hurls an insult Don’s way the slur cuts him to the bone.

After belittling Peggy and Ted’s relationship and threatening to expose the affair to a client she calls her mentor a monster. Peggy knows what makes Don tick. She can often see the real man behind the curtain. Perhaps hearing that hard truth from someone he truly respects and who truly knows him is just too much to take - as evident by the sight of Don curling up in the fetal position after a furious Peggy leaves the room.

PEGGY ASKS FOR THE BAIL MONEY BACK

Don is involved in an alcohol-related accident and gets busted for drunk driving while out with his mistress. The junior copywriter comes to the rescue, bails her boss out of jail and even offers to let Don’s girl stay at her place while recovering from injuries.

Peggy is loyal and will not divulge Don’s indiscretions but when the time is right requests Don reimburses her for the bail money. Upon payback, she thanks him by using his first name -letting Don know if he’s going to trust her with such secrets they should at least be on equal footing.

DON PROMOTES PEGGY

For much of season one Pete Campbell was a thorn in Don’s side and threatened to expose his true identity. Pete, who is in a committed relationship, also had a fling with Peggy and proceeded to treat her like dirt.

After Pete lands a big account for the agency Don decides to kill two birds and immediately promotes a beaming Peggy to junior copywriter and puts her on Pete’s new account - infuriating the young executive and reminding him who runs things at the agency.

DON ASKS PEGGY TO JOIN NEW COMPANY

When Don hatches a plan to leave the mothership and start a new agency rather than get swallowed up by McCann he just assumes his star pupil will go along. But when he asks Peggy she does not immediately jump at the idea and is unsure if she wants to spend her career trying to live up to Don’s enormous expectations. She asks Don if he will hate her for not going along to which he replies, “I will spend the rest of my life trying to hire you.” Sensing Don truly needs her, Peggy agrees to join the new agency.

DON VISITS PEGGY IN THE HOSPITAL

At the end of season one Peggy wound up in the hospital with terrible stomach pains and to her surprise found out she was pregnant with Pete’s child. The audience is unaware of exactly what happened next other than Peggy returned to work thinner and without a child.

It is revealed through a flashback that a groggy Peggy was visited in the hospital by a concerned Don. While he didn’t ask too many specifics he gave one piece of advice that Peggy took to heart - move forward.

PEGGY QUITS

Peggy feels under-appreciated and is tired of trying to live up to Don’s unbelievably high expectations. She receives a generous offer from a rival company and decides to quit. Upon telling Don he first laughs it off before realizing she is serious. Fear sets in and Don throws money her way but Peggy stands her ground and says goodbye while holding back tears. Don is also visibly shaken and realizes-albeit too late-how much Peggy is truly worth.

THE SLOW DANCE

Peggy and Don have worked together for so long they know each other as well as a long-married couple - perhaps more.  But in the season seven episode, “The Strategy” they reveal some pretty deep stuff while working late into the night.

Peggy talks to Don about being a mother while he shares his fears about ending up alone. The evening ends with the two slow dancing tenderly to “My Way.” If there was ever a moment audiences were expecting some passion between the two this was certainly it. But the duo is smart enough to know that would ruin the good thing they have.

THE PHONE CALL

In the Mad Men finale titled “Person to Person,” Don Draper makes three very important phone calls. One to his dying wife, one to his daughter and one to Peggy. She is angry at first, not knowing where Don has been for the past few weeks since he just disappeared from the office.

After a few minutes, anger turns to concern and Peggy tells her mentor to come home. Don is on a soul searching mission and not ready to return telling Peggy he only called because he needed to hear her voice.

PEGGY COMFORTS DON

Don forces Peggy to work overnight with him on an important account. But in reality, he just needs a distraction. He missed a phone call earlier in the day from California and fears it was bad news about his sick friend Anna. The two sleep in the office and in the morning Don finally returns the call only to find out his worst fears are true - Anna has died from cancer.

Overcome with grief Don breaks down in front of Peggy. She is surprised at first but then offers comfort. Don tells Peggy that someone very important just died and refers to Anna as “the only person who really knew me.” Peggy gently rubs Don’s back before offering an encouraging truth, “That’s not true.”