Ensemble Darkhorse: Mary actually became one for some fans after she left the show, mostly because anyone that could incite that much annoyance and whining from the Camdens had to be alright. Especially prominent once Annie stopped bothering to hide that Mary was The Unfavorite, since by then Annie had become a Jerkass.
Family-Unfriendly Aesop: Many, i.e. the classic "Obey your parents' wishes about how to celebrate getting your first period, no matter how uncomfortable it makes you feel."
Fridge Logic: In the episode X-mas two young women are afraid that they don't know enough about the religious aspects of Christmas, and that the Camdens will realize this. Anybody who grew up in the United States could tell you that it is practically impossible to avoid the story of Christmas growing up, especially around Christmas time. Made even more ridiculous when one of the girls doesn't even know what a nativity scene is, and assumes that the people in it are begging for money.
The Season 4 episode "Talk to Me" (involving Eric counseling a young girl who had been molested) falls into this after the release of a recording in which Stephen Collins (who played Eric) admitted to having sexually molested 3 young girls.
The Season 4 episode "Yak Sada" includes a well-intended storyline in which the Camden women protest the social standing of women in Afghanistan. Given that this episode aired in 1999, it's downright bizarre watching the reverend have to pause and think to come up with the group repressing them - the Taliban.
The Season 2 episode "I Hate You" opens up with Simon asking Eric where he was at the Kennedy assassination, which he considers the "world's greatest 'Where were you when...' question" which comes back to bite him in the butt when 9/11 came around only a couple of years later.
Allison Mack here portrayed a character who cut herself. In 2017 and 2018 it was revealed Allison was a victim and an accomplice of a sex cult that branded women with Keith Raniere's initials, and was a very broken person.
Lucy's storyline where she miscarried twins becomes twice as depressing when her actress Beverly Mitchell revealed that she herself miscarried twins in 2018.
Martin's introduction has him skulking around the Camden house and then, bizarrely, coming inside and helping himself to food despite not knowing anyone there. His actor Tyler Hoechlin later played Derek on Teen Wolf (TV series), a character infamous for his habit of stalking teenagers and appearing in people's rooms with no warning.
The episode “Gossip” that guest stars the Olsen Twins has Ashley Olsen’s character named Sue Murphy.
The Season 2 episode "Who Knew?" involves Matt coming home with a joint (which he got from a friend, though Matt didn't actually want it), which is accidentally found by his father, who then suspects almost all of his children of having brought the joint into the house. The plot could've been averted if Matt had just thrown away the joint immediately after getting it (he never wanted to smoke it anyway, so why keep it?).
Part of the Season 6 episode "Relationships" involves Annie's (brief) job as a teacher being threatened by a student's parents after she indirectly suggests that they should divorce. The problem is that Annie could've told the principal that it was a misunderstanding, considering that the student didn't mention her parents during the conversation, and Annie believed that it was between her and a little boyfriend. Failing that, she could've told the parents the same thing beforehand, and much of the plot would've been avoided.
Moral Event Horizon: Many fans thought Annie crossed it when she threw the twenty-something Matt and Lucy and the then underage Simon and Ruthie out of the house and forced them to live in the unfinished (read: no furniture or plumbing) garage apartment until they agreed with her opinion that Mary coming home was a good thing. Ironically, Mary eventually became The Scrappy and general "disappointment" of the Camden family in later seasons and Annie would pretty much cringe if you even mentioned her name.
Pandering to the Base: What some have assumed the show creators to be doing, essentially crafting a show to appeal to a demographic that most other shows have nothing but venom for. Things like the abovementioned point in Fridge Logic don't make much sense... unless they're less trying to reflect what they see as reality and instead prey on the fears of the religious (that "Christ has been taken out of Christmas"). Considering the sheer amount of Narm, you could almost interpret the show as a Stealth Parody or Take That that kept itself low-key enough to be loved by the people it was actually mocking.
The Scrappy: Kevin with the fans, Mary with the writers. Simon's girlfriend Cecelia (Ashlee Simpson) wasn't too well-received among fans either.
Many viewers dislike Lucy, seeing her as very bland, self centered, and whiny.
Fridge Brilliance (of a sort) kicks in when you realize that they were trying to portray Lucy as growing up to be just like her mother. Without quite realizing that a lot of viewers thought her mother was a terrible person.
Ditto for Mary, even Jessica Biel'shotness can't cover up that she's can be a bit of a bitch.
Many dislike Ruthie as well, and see her "cute" antics as bratty.
Any of the non-Camden main cast in later seasons got this because many fans felt that they were unnecessary for a show that's supposed to focus on a family. Ruthie's friend/boyfriend Peter and his mom Paris, Kevin's partner Roxanne, associate pastor Chandler, Martin(though he was later Rescued From the Scrappy Heap when he became a potential Love Interest for Ruthie), Ruthie’s other less liked Love Interest T-Bone, Cecilia’s adopted sister Meredith, Simon's bitchy girlfriend/fiancé Rose and Martin's baby mama Sandy are some prime examples of characters that received a lot of hate from the fandom during their time on the show.
Seasonal Rot: Many fans thought the show started going downhill around the time season 6 started.
Snark Bait: Read the Television Without Pity recaps! Before the 'cappers ultimately began vomiting at the sight of the show, of course.
Tear Jerker: For a show full of Narm, there actually were some truly heartbreaking moments:
The death of Annie's mother early on in the first season. Her father also passes away in the 8th season and it at first seems like Narm, until you realize the actor who played Annie’s father passed away in real life.
The ending of the episode "Lost" has a Crowning Moment of Heartwarming by reuniting a kidnapped child and his family, but shifts into Tear Jerker territory when the usual ending credits are replaced with photos and details of actual missing children.
The whole entire plot of "Nothing Endures But Change", which is made even more heartbreaking when you learn that its plot, concerning Lucy losing a friend in a car accident, is based on the real life death of Beverly Mitchell's (the actress who plays Lucy) friend in a similar accident.
Chandler's breakdown in "Smoking" is also pretty sad, though it may border just a bit too close into Narm territory for some.
On the Put on a Bus episode for Mary (Mary was turned into a bit of a troublemaker to facilitate Biel's departure), Simon and Lucy tell her that they care for her very much and want to help her in any way because they look up to her. Then Ruthie's turn comes up, and basically lays into Mary for being a selfish sister who's let her down and angrily leaves the room. The fact that the What the Hell, Hero? speech came from the youngest, precocious sister was startling and moving (and probably mirrored the writers' feelings as well).