In Appaloosa Plains from the Pets expansion pack, it’s heavily implied that the Singleton family had a horse die due to improper care. The player can also neglect their pets, but they will be taken away by social services if this happens.
Pets can die, but they get the nicest death animations where it shows them playing with the grim reaper oddly sweetly and then going to animal sim heaven lol.
In the Pets expansion pack you can find snakes in the wild and keep them as pets. In the World Adventures expansion pack there's a snake charming basket.
It is, however, a recurring joke in the series that male Sims can be abducted and impregnated somehow by aliens (nothing is shown; the Sim is beamed up and then returned). I don't exactly recall if that's present in this game, but it's something to be aware of.
Sims can die from catching on fire. However, it is not very graphic and can in fact look comedic (the game isn't very serious), they simply wave around wildly and other characters nearby will attempt to put them out.
In The Sims 3: Supernatural expansion pack, there is the possibility of being cursed as the Tragic Clown". There are also paintings of clowns and clown toys available.
With the "Showtime" expansion pack, Genies can "ensorcel sims" outside of the active family and take over their actions. The player is entirely in control of this.
In the Sims 3, vomiting occurs after eating food that is off, in the early stages of pregnancy (before the Sim knows that they are pregnant), or after certain mishaps including failing to make a potion in the Supernatural expansion or sometimes after flying a jetpack in the Into The Future expansion.
If your Sim does not go to the bathroom before their bladder meter goes all the way down, they will wet themselves. This can be avoided by going to use the toilet before the meter runs low, or by using cheats
In the Into the Future expansion pack, sims with the unstable trait can be admitted to a hospital for mental episodes. However, the inside of the hospital is never shown.
Sometimes when you adjust the weight sliders, sims will vocalize and look down at their bodies. This happens for sims with more or less body but it could be triggering for some.
Your pregnant sim will "go into labour" after 2 days of being pregnant. They can either go to the hospital which is a rabbit hole, so nothing is seen or heard, or if you cancel the action they will "give birth" at home. All this is is your sim holding her stomach and breathing/groaning. It's not as graphic as I'm making it sound. Then she spins around and bam, baby magically appears in her arms. You can fast forward through it or move the camera somewhere else.
Sims are separated by age group rather than a specific number. All adults (Young Adults, Adults, Elders) may engage in romantic relationships with each other. Teens may only engage in romance with other Teens. Anyone younger cannot engage in romance whatsoever. Age gaps do exist, however all parties are able to consent.
In The Sims 3, it is possible to die by drowning, although it's much less likely than in previous versions of the game as now characters can get out of the pool even with the ladder removed.