At it's core Parks and Recreation was about the relationships between the main characters. Well, that and adorable mini horses. But one relationship that many fans were never on board with was the one between Ann Perkins and Mark Brendanawicz. It ran through most of Season 2, coming to an end in a seemingly sudden faction. In reality, their breakup had been heavily foreshadowed episodes earlier.
Both Ann and Mark were introduced in the first episode of the series. Mark, a city planner, was working with Leslie Knope, who had a huge crush on him. Ann was working as a nurse and was in a long-term relationship with Andy Dwyer. The fact that Andy had fallen into an open-pit by Ann's house caused her to attend a public forum that Leslie was running. This quite literally led to Ann being introduced to the Parks crew.
By the beginning of Season 2, things had changed quite dramatically. Andy and Ann had broken up, with a homeless Andy taking up residence at the bottom of the pit that had once broken his legs. That was actually quite on-brand for him and was the beginning of his upward climb. The man literally could not have gotten any lower in his life without a shovel or a backhoe, so there was nowhere else to go but up.
What was not on-brand was the burgeoning relationship between Ann and Mark. She had been incredibly clear in Season 1 that she did not like Mark. Yet, she had changed her mind between the two seasons. Ann admitted to growing fond of Mark while helping him recover from falling in the pit in Season 1, Episode 6. It was a very clear case of the Florence Nightingale trope, where a caregiver falls in love with their patient.
The problem for Mark was what happened when that effect faded away. In Season 2, Episode 22, Leslie was working on a telethon in Pawnee. Ann tried repeatedly to talk to her, and when they finally managed to have a conversation, Ann filled in Leslie on the fact that she was exceedingly unhappy with Mark and wanted to break up with him. This was kind of an issue, as Leslie has just convinced Mark to propose to Ann live on air. But she solved that problem by flashing her butt at the camera.
This break-up had been thoroughly and completely foreshadowed in Episode 20. Tom Haverford was taking pictures of Ann and Mark together for the cover of the Pawnee Summer Catalog. As he did so, he kept complaining that Ann looked unhappy. It was so obvious that when Mark saw the expression on Ann's face in the photos, he asked her what was wrong. Ann honestly didn't have an answer at that time, but fans could see that the wheels had started turning in her head.
It was in that moment that Ann started questioning her relationship with Mark and the Florence Nightingale effect almost instantaneously faded away. For anyone paying attention during Episode 20, the break-up in Episode 22 was anything but a shock. On Parks and Recreation, things rarely came out of the left field and almost everything was set up episodes in advance. Mark was the only one who was surprised.