Mac and Stella. You could literally hear the hearts of many "Smacked" fans shatter into a million pieces after Melina Kanakaredes decided not to return for season 7.
Mac/Jo replaced it, though it caused Ship-to-Ship Combat with the Smacked shippers and the fans of Mac's girlfriends (first Peyton, then Aubrey and finally Christine).
Franchise Original Sin: Mac Taylor and Jo Danville are seen unintentionally unsympathetically for their constant decision to ignore the failings of the systems in cases involving people who were made the way they were because of the system's failures. "Prey" in Season 5 featured a case just like this, with a stalking victim named Dana who did everything legal to get away from her stalker, but the law was too weak to punish her stalker significantly. He inevitably found her, at which point he started escalating to violence, and so she killed him since the system already failed her. Mac does lean on his usual "murder is murder" belief, but at the end of the episode, is clearly sympathetic to Dana, and even admits that arresting her is one of the more difficult parts of the job. Unlike future seasons, this episode acknowledged that while killing him may not have been necessarily right, but made it clear that circumstances left her with few other choices.
Fridge Logic: If Adam and Lindsey were in "The Pile" for weeks after 9/11 and around chemicals the rest of the time wouldn't their health be a lot worse?
Season 9 features an episode where a little girl dies by her friend accidentally shooting her. He'd already removed the magazine, so assumed it would be safe. Cut to a previous episode featuring Jo finally taking down a rapist she's been trying to catch since her days in the FBI. Her words at that time may echo in your head watching the scene with the kids. "They always forget the [bullet] in the chamber."
Sid being diagnosed with non-Hodgkins' lymphoma becomes this when you realize that Hawkes' actor Hill Harper battled thyroid cancer at one point and did a book about it, but thankfully has since gone into remission.
Season 9, and the entire series, ends with the police shooting an unarmed Black man, Timothy Brown, leading to large protests. Barely a year later, a Black man named Michael Brown was shot in Ferguson Missouri under disputed circumstances, leading to major protests by Black Lives Matter.
Mac’s kidnapping in season 4’s finale didn’t scare most fans since Gary Sinise had another season in his contract.
Christine in the crossover episode. Most fans didn’t really feel she was in any danger especially with the feeling the series probably wasn’t getting a 10th season.
The Problem with Licensed Games: The game wasn't as good as the others in the franchise. It isn't totally awful, but for some reason was mostly puzzles and hidden item stuff as opposed to the more detailed evidence collecting, tests, interviewing, etc. of the other two shows. Plus, the puzzles can frustrate to no end, especially the "draw a line without touching the non-matching items" one and the "draw the outline" one for some. Plus, each case was short and Mac and Stella were the only player characters, as opposed to either all of the team at various points or a original player character like the rest. And fans tend to view it as yet another example of the show getting the short end of the stick.
Frank Grillo appeared in the conclusion of the 333 Stalker storyline as the brother of said stalker before playing Crossbones.
Before appearing in Suits and later getting engaged to Prince Harry, Meghan Markle appeared in one season 2 episode and also appeared in an episode of CSI: Miami.
Jamie Chung appeared in the penultimate episode of the 333 Stalker storyline.
T.J. Thyne played a rare book dealer and killer of the week just a year before starting his regular role on the other side of the police, er, FBI tape as Dr. Jack Hodgins on Bones.
Danny/Lindsay, referred to as "M&M" (Monroe & Messer) and probably should now be called "3M" or "M cubed" (Messer Monroe Marriage-or possibly 3 Messers, as in Danny, Lindsay and Lucy.) Of course, once the second baby arrives, it could be 4M...you get the picture.
Flack/Angell has a pretty vocal contingent as well (including many shippers who are royally pissed at the season 5 finale).
Mac/Stella is also a favorite among fans. However, many shippers were either sad and/or angry because Melina Kanakaredes didn't come back for season 7.
Mac is in the middle of most of it. Some want him with Stella, others with Jo, and others say no one can take Claire's place. A few slash ships get in, too. Turns his girlfriends into The Scrappy sometimes. Very few people wanted him with Peyton, but Christine, his canon girlfriend as of season 8, isn't hated as much and adds another layer to it. However, in all the cases, no extreme hostility is usually evident.
May intensify a bit with Mac marrying Christine. Expect a few fics to show up trying to get rid of her in favor of the other ships.
Sometimes, other ships gang up on Danny/Lindsay; most often, these are shippers of Danny/Aiden, Danny/Ricki (the woman whose son was killed on Danny's watch), and especially Danny/Flack. These shippers perceive Lindsay to be The Scrappy and accuse her of changing Danny too much from his previous "bad boy" persona, inhibiting his character development, and having "too much" screen time. They would like to see Danny with "anyone but Lindsay."
They Changed It, Now It Sucks!: Aside from the typical complaints about new characters, this popped up when the producers overhauled the storylines after a few seasons to replace some of the dark, gritty, weird stories with more upscale rich characters and settings. Eventually, new ones tended to get "What, another rich victim?" every time one was announced.
They Wasted a Perfectly Good Plot: Some fans felt that it would've been interesting to have a "CSI: New Orleans" spin-off focusing on Stella, following her departure between seasons 6 and 7.
A recurring element of the series is members of the main cast, Mac Taylor and Jo Danville in particular, telling perps that Freudian Excuse Is No Excuse, that they didn't have to resort to murder and should have relied on the system. This is in spite of the many examples of the system failing victims and being the reason some perps became the way they are. The episode "Crossroads" in particular stands out, as Jo tells the perp of that episode, a young man whose life was ruined by a Hanging Judge who sent him to prison for a kickback, that he should have just trusted the system, ignoring the fact his victim was rigging the system, and it was said system that screwed him over in the first place, making Jo look like she doesn't give a shit and only cares that someone was murdered.
The "John Curtis" arc doesn't do Jo Danville any favors. Throughout the arc, she regularly makes clear she's a By-the-Book Cop who went as far to fire her ex-partner, Frank Waters, after he mislabeled the DNA sample and tried covering it up, simultaneously tanking the case against the eponymous rapist. Her reiteration however only made viewers see her as acting Holier Than Thou while also being a total hypocrite, since despite being told by Mac not to get involved with the new case against Curtis, she keeps inserting herself into the investigation and acting like she's in the right. Her treatment of Frank likewise makes her look heartless due to firing him over a single mistake while preaching about her "ethics" and placing the blame for the original case tanking solely on him, same for when she snaps at Lindsey for a poor choice of words while ranting about how she did the right thing.
Adam, especially for the amount of screen time he gets. He gets very nervous and lacks confidence around authority because his father was a 'bully', which leads him to often embarrassing himself in front of Mac and Stella, two of the people he respects the most. In the season 3 finale he was tortured for hours, which was probably a nice reminder of his childhood and almost shot by Flack. Not to mention the guilt he must have from watching Danny get absolutely whomped to save him. In Green Piece, he's playing a pick-up street hockey game and a van on the street he's playing on explodes and after saving someone from the explosion, while concussed he gets to be interrogated by Mac. Adam also thinks he is being fired by Mac; luckily it was budget cuts from on high and Stella and the team help out, but not before we get to see some Emo!Adam and two seasons later he still thinks it might happen. In season 9, he witnesses a murder online, gets beat up again, and has to deal with his father having Alzheimer's which, of course, brings up his childhood issues again.
Possibly Danny as well, although he doesn't have the kicked puppy thing going like Adam does—he just can't catch a break. He undergoes a spectacular fall from grace in the first season, to the point that Mac takes him off the promotion grid; second season his brother gets beaten into a coma trying to clear Danny's name after Danny gets implicated in a murder his brother was involved in; gets "absolutely whomped" on in the third season finale (see Adam above); and in the fourth season he sends a kid he's fond of away from a crime scene to keep him safe, only to have it turn out later that the kid had been shot without anyone realizing, and died of blood loss. Danny has massive guilt over this for the rest of the season. Later, his badge is stolen and used by a serial killer who stalks his family and ends up holding his toddler daughter at gunpoint.
