These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ear Worm: Given enough time, you will have the loading/neighborhood and buy/build music burned into your memory. Not helping matters is that every other expansion or so introduces a new version of some of these tracks to fit with the pack's theme (college marching band for University, electronic/techno for Free Time/Open for Business, tropical for Bon Voyage, etc).
Many players enjoy improving Lilith Pleasant's life, often at the expense of Angela's.
And it seems like some players like the Townie Goopy, maybe because of his name and his big nose.
The Pleasantview Goths and Strangetown Curious family are pretty popular.
Kaylynn Langerak was an NPC with a minor story role in The Sims 2, but it made her popular enough to merit a promotion to playable character with her own extended family in The Sims 3.
Building off this, there's a sizable minority of players who prefer to marry Mortimer to Kaylynn instead of his canonical wife, Bella, in The Sims 3. The two most commonly cited reasons are Bella's ubiquitous place in the games getting annoying, and fans being upset by a throwaway comment in the PSP spin-off suggesting that Bella only married Mortimer for his money.
Evil Is Cool: Oh, hell yes! A Sim with the evil trait can amongst other things donate money to counter-charities, look for evil deeds and stars in the telescope, do an Evil Laugh every time another Sim dies, steal candy from babies and children, and Troll forums. Good Is Boring in comparison.
Additionally, Evil Sims can take an Evil Bath or Evil Shower.
They also get a positive moodlet ("Fiendishly Delighted") if another Sim in the room is unhappy.
Fan Dumb: Mentioning that you like (or dislike) a given EP can result in a full-fledge Flame War. Some people love TS3, other despise it with a burning passion. Finally, never even mention "paysite" or "Garden of Shadows" to a The Sims fanbase member without knowing their opinions about the aforementioned. Let's not even get started on how the Official The Sims BBS/Exchange and its casual gamer casual population is viewed by more devoted fansites.
Never, ever ask the forums of a certain The Sims Game Mod forum for help in navigating the labyrinthine process of installing said Game Mod. Because everyone who has a problem with it is an idiot, naturally, and not at all because it's trivially easy for said Game Mod to generate Game Breaking Bugs if you even look at it funny.
Fanon: A little bit. For example, Frances Worthington is played as gay in many stories, and the townie Meadow Thayer is said to be "the neighborhood bicycle". Also, in fanfics usually there is some sort of connection between Strangetown and Pleasantview (because Bella Goth can be found as a townie in Strangetown), and usually Lilith Pleasant is seen as the better twin, while Angela is seen as a Mary Sue.
Once you got the robotic butler/maid in The Sims 3, it would efficiently remove all worries about cleanliness, repair and so on, freeing Sims time much more for other goals.
This seems to happen with every new expansion pack. Generations gave us the motive mobile, a car that fills every motive of the Sims riding in it. You don't even have to ride for long in it. Another expansion also gave us the "Age Freeze" and "Young Again" potions, which do exactly what their names imply (the former can only be used on teen and up while the latter is only for young adult and up).
The "Master of Seduction" lifetime reward. Buying this ensures that romantic interactions never fail, making finding a romantic partner a breeze.
The dragons introduced in the Dragon Valley premium neighborhood are all but legitimized cheat items. You can sell the hatched dragons for more than the cost of the egg, each dragon colour provides a unique moodlet when interacted with that refills and prevents the decay of two needs, and each dragon type can be talked with to boost a single skill up to max effortlessly, among many other effects unique to each dragon type.
The Moodlet Manager in Sims 3. It can be used to "Cure" negative moodlets. How is that overpowered? Because it can also remove moodlets caused by low Needs, like being tired. If the moodlet gets removed the Need is immediately filled to the max, effectively removing the need of Sims to eat, sleep, wash etc.
Supernatural added the Alchemy skill, which allows anyone with the right ingredients and enough skill to make some truly game-breaking potions. There are potions to refill and freeze your Sims' fun/social or energy motives, increase random skills by one level the next time they sleep, or even drop them back to Young Adults instantly. Even money becomes a non-issue with the Touch of Midas potion, which allows your Sim to turn anything into gold and double its value.
University of Sims 3 a added the Science skill, that allows anyone with enough skill to duplicate most things. Because using the Group Science Project correctly would make some ores fall from the sky, and at least one of these ores could be a precious high-priced ore. Send it to be smelted, and your Sim(s) now have mostly infinite amount of cashes.
Hollywood Pudgy: Female "fat" Sims, with only a slightly wider waist than the rail-thin "normal" Sim ladies, somewhat larger boobs, and Hartman Hips (or at least they're Hartman Hips compared to regular female Sims). Male fat Sims are kind of similar; they have potbellies, less muscle definition, and slightly larger thighs, but that's all. And both sexes are lumpier of build than the regular Sims. The second game is the worst offender, although the third averts it.
It's Short, so It Sucks : Some fans consider The Sims 3 expansion packs to be rather lacking in content. This is most apparent with Late Night and Showtime, two expansions which make up two halves of the content of one The Sims 2 expansion (Nightlife).
Jerkass Woobie: Nervous Subject. He might be a mean, antisocial slob with no sense of humour, but he was neglected as a child and used by his 'adoptive parents', the Beakers, who are also very mean, for experiments. He's a Family Sim, and is a far more capable babysitter than the nannies the game provides (though that may say more about the nannies than Nervous Subject himself).
Mary-Sue Pleasant could be considered a deconstruction of the trope. She's so obsessed with her job that she doesn't notice her husband's affair with the maid, or the fact that her twin daughters hate each other.
Also, the majority of female Sims put on the Exchange have a description like "omg this is Jennifer she is so kewl and awesome and pretty please download!!!!!!11"
"Jamie Jolina is an intelligent as she is beautiful. Can she prove to the world that two traits can coexist?"
Most Annoying Sound: The relentless honking of the carpools in The Sims 1. We get it, you're stuck/want our Sims to go to work!
Most Wonderful Sound: Several, one example being the little tune that plays when obtaining Pangu's Axe.
The hula zombie music. It IS a death theme, but it's still surprising how eerily spooky and depressing it is.
Scapegoat Creator: The disproportionate scorn heaped upon Rod Humble, at one point executive producer of the Sims division, because of his past experience working with SOE and some offhand comment that he "didn't get The Sims at first". Fan Dumb feared he was going to "turn The Sims into EverQuest." It didn't help that he appeared as a Sim in one expansion as essentially a door-to-door hype salesman.
The Scrappy: The social worker, Mrs. Crumplebottom, and Angela Pleasant.
Miss Crumplebottom was hated for a very long while... however this changed in The Sims 3... (see Tear Jerker), but Mrs. Crumplebottom is still as hated as ever.
Marsha Bruenig: a townie in Pleasantview. Once you meet her, she will NEVER stop calling, even at night and during school! Simmers actually regard her with fear.
A lot of Simmers are annoyed by babysitters in The Sims 3 because they will either neglect the baby or constantly bother him/her when all needs are full. Also, if there is a baby swing and the baby is in it, the sitter will often set the swing on fast, making the baby cranky and sick.
The Ottomas family from Seasons. They are ugly, bugged, can even corrupt the game, and Samantha gives birth to the most hideous twins in the world.
The newly implemented Memory System in The Sims 3. It was a return of the Memory System of The Sims 2 in which Sims would get memories added to their book whenever something significant happens in their life. Instead, Sims would get memories for almost everything they do. Went to buy something? Memory! Just unclogged a toilet? Memory! Passed by the library on your way to work? Memory! It doesn't help that you get an incredibly annoying pop-up saying that your Sim obtained a memory every time this happens. Fortunately the developers had a heart and allowed you to disable the pop-ups, but not the memories. And with the Seasons patch, they finally allowed disabling memories.
But wait! It gets better! Inactive Sims would also gain memories. Did I mention memories take up space in your save file? If you've noticed that your game is loading/saving slower than usual after installing Generations, it's probably the game trying to process all of your memories. It's not surprising that within a week or so of this new system, mods immediately popped up to stop the memories.
Also the Romantic Reputation system in The Sims 3, which causes spouses to declare Sims a cheater simply for interacting with another Sim.
It gets quite juvenile in some situations. For example, did a Flirty Sim decide to bat an eye to your Sim? Your Sim's spouse will then call you a cheater and proceed to reject all social interactions with you and even break up with you afterwards.
Then there are celebrities and vampires in the Sims 3, which quickly becomes an uncontrollable plague. Thankfully, Supernatural and its accompanying patch give you the option to prevent them from spawning.
By becoming a celebrity, even by accident, even with the celebrity spawning turned off, your sims are potentially subject to scandals that give them a negative moodlet. Oh, and they also damage their relationship with every sim the effected sim is acquainted with regardless of the absurdity of the claim. This can often lead to half the town hating your sims for no real reason. You can offset the loss by personally interacting with each individual sim to assuage the rumors, and to sue for slander.
There's also the Ice-Cream truck introduced in Pets, who will frequently park in front of your home lot and stay there for hours like a stalker. Also the Paparazzi from Late Night, though they won't bother you unless you're a celebrity.
The "room" meter. Almost always keeps the Sims away from obtaining a perfect mood, and even in a very well-designed house, they still have it half-red.
Supernatural added zombies which never stop coming and constantly attack your furniture. It is pretty much impossible to have a garden now without freezing the lunar cycle (the closest option you have to turning it off entirely.)
A simple trick to safely garden is to build a perimeter or fence, then add a fence door. Left-click the fence door, left-click to "Lock...", and choose "Everyone but me" or "Everyone but my household."
Seasons continues the downward spiral of Scrappy Mechanics, with the attraction system which has The Most Annoying Sound to go with the hotties attraction towards your Sim.
Pregnancy in The Sims 2 causes hunger and energy to deplete at such an acceleration that failure to juggle both adequately is quite likely to prove fatal unless you micromanage like crazy. (Giving birth is 100% safe in the Sims' world, but pregnancy cravings can be a literal killer.) Gets even worse with Nightlife installed, as you'll often find yourself in the extremely frustrating position of watching your pregnant Sim starve to death after she (or he) falls asleep face-down in a plate of food. Luckily, the pregnancy mechanic was overhauled comprehensively in The Sims 3 to prevent this from happening.
The mechanic in The Sims 3 whereupon a new neighborhood is automatically populated with expansion and patch content buildings (Showtime venues, consignment stores, ect) when created. These new buildings occupy empty lots, seldom (if ever) match the neighborhood theme and are often placed haphazardly by either facing away from the street or smack dab in the middle of a large lot. This can leave a simmer spending several minutes after loading a new neighborhood rooting out, deleting and then repurposing the resulting empty lots so their towns don't look ridiculous. There is no way to turn this feature off, unlike methods to circumvent other scrappy mechanics.
Stop Helping Me!: The Nanny NPC can be like this. She usually will a) not take care of your children at all, instead she will bake cakes (and ignore them if the baby starts crying, thus causing a fire) or watch TV Or b) she will pay too much attention to the baby, waking them up to feed and bathe them (when their hunger or hygiene motives are full), and then putting them on the floor instead of in a crib.
Suspiciously Similar Song: Averted in The Sims 2: Open For Business, where a new radio station is added entitled "New Wave", which features acts such as Depeche Mode and Howard Jones - who actually rerecorded their 80s hits in Simlish for the game.
In The Sims 3, Agnes Crumplebottom, the woman who grows into the old and alone Miss Crumplebottom from Hot Date that we hate so much, has one as her back story. Her husband drowned on their honeymoon, leaving her alone and mourning in their mansion built for three, too grief stricken by his memory to try looking for a new suitor. In the upstairs of her house, she still has a nursery room that is only half finished. Because of the tragic nature of her back story, it's popular amongst players to revive her husband with the use of ambrosia and give her the happy ending she deserves.
Heck, any time a Sim dies, especially if you're one to get attached to them.
They Wasted a Perfectly Good Plot: Despite having accumulated many, many characters over the years with The Sims and The Sims 2, EA insists on creating boring, unmemorable Sims for The Sims 3's neighborhoods instead of reusing the older ones.
Uncanny Valley: Many of the custom mods (specially the ones to simulate celebrities) give more detailed skins, eyes, hair, etc... it can be a little disturbing.
To some, the Sims in The Sims 3 are like this. While in The Sims 2 they were realistically animated and proportioned while still having cartoonish facial expressions, The Sims 3 attempts a realistic look which just makes Sims look like vacant, dead-eyed zombies. They also tend to react in ways that seem like they're not sane.
The Sims in The Sims 2 can be considered this as well. It's the extremely detailed teeth that do it, not to mention that some Sims lack eyebrows...
The "Pregnant" moodlet in The Sims 3 has come under criticism (for example in this article at Cracked.com) for automatically giving pregnant women massively positive moods due to the fact that "creating life is wonderful" etc. etc. - perhaps not too egregious in itself, and probably actually put in place to combat the above mentioned Scrappy Mechanic that was pregnancy in The Sims 2 rather than for any more insidious reasons. The problem really hits when you factor in that even women with the Dislikes Children trait are apparently over the moon during the whole of their pregnancy, and that even a massive mood hit like the death of a family member can't put a dent in their pre-natal joy; the whole thing becomes a bit too Stepford Smiler meets Baby Factory at that point.
Who Wants to Live Forever?: The Age Freeze Potion you can buy with lifetime experience lets you experience this trope in full effect.
The Woobie: Basically every Sim that has the loser and/or unlucky trait. Even Death takes pity on the poor sap; both provide immunity to death by anything other than old age. The drawbacks for both are pretty light, so it's really a case of Cursed with Awesome...
Death doesn't actually take pity on Unlucky Sims when he revives them. Instead, he laughs at their constant mishaps and doesn't want to take away such hilarious entertainment too early.
Also Bella Goth, to an extent.
Lilith Pleasant and Ripp Grunt, the famous unfavorites.
Agnes too. She wanted to have a perfect family life with her new husband, and he died. They even had a nursery. Now she lives a depressed life and becomes the purse-wielding grump we know in Hot Date.
The Newsons from Apartment Life. They're a family of adopted children whose parents have died, and the two teens have to juggle school, caring for the younger ones and providing a steady income. Unless you move them in with an adult Sim of course.