Anvilicious: Practically every case that Regina comes across in Season 4 has to do with parenting or children. She had just happened to become pregnant, and was having some serious doubts about it.
the ending to episode 3 of season 3; we learn that Sherman's mother wasn't actually being raped when his front teeth got knocked out, the sex was consensual as she was doing it to pay off Ben's father's drug debts. I mean really, who saw that coming?
The last episode of Season 5: John Cooper comes back to his ex's house who complains about a neighbor's noisy generator keeping her up at night. He goes to confront the neighbor, who calls the cops. Said cops come and Cooper pulls out a gun, forcing the cops to shoot (Word of God says he survived). One of the cops recognizes Cooper, pointing out that he's a highly decorated LAPD officer. This would turn out to be the final scene of the entire series.
Seasonal Rot: Season 4 verges on it with a weak Detectives' season arc but is held up by the partnership of Cooper and Tang and how it collapses. Season 5 is generally considered weaker than the rest, however.
The kid who begs Cooper to adopt him. And then Cooper's breakdown at the end of the episode.
Cooper saving Mike and telling him that it gets better. Sadly, it's not enough to save him and Mike jumps off the roof of the hospital.
After Cooper and new partner Lucero earlier bond over some drinks (at a gay bar, no less) the next day's shift brings kidnapping, torture and the sudden murder of Lucero by two meth heads.
And Cooper's spontaneous almost-suicide-by-cop after the conclusion of that incident, in what would prove to be the series' final scene.
