- Annoying Video-Game Helper: Will Wright himself in the Turbografx version. The main reason he's annoying is because the advice he offers on each scenario isn't very helpful (over the years general strategies for each scenario have emerged, and none of them match what Will Wright suggests. Ironically even though Will Wright wrote the game, he apparently isn't very good at playing it.)
- Character Tiers: Enforced due to different species having different likelihoods of attaining sentience. Robots are the most likely if introduced. Below them are mammals and dinosaurs, the most likely sentient species to occur by laissez-faire play. At the bottom are Trichordates, which even The Monolith will frequently fail when used on, and below even that are Carniferns, which not only need specific conditions to appear in the first place, they are very difficult to control enough to develop intelligence before another species beats them to it. Still, though, sentient carniferns.
- Fridge Logic: Traveling sentients can be seen riding horses or horse drawn carts, even if mammals do not exist on the planet.
- Funny Moments: What's the one thing that can halt a robot infestation singlehandedly? Daisies.
- Game-Breaker: The Monolith, which allows you to choose a sentient species rather than wait for evolution. Risky in scenario levels due to the high energy cost — and soft-disabled in Hard planets by costing more energy than the Cap can hold — but not in modes where energy isn't a factor.
- Nightmare Fuel:
- It's possible (and common, if the monolith is used too early) for intelligent life to completely die out. If this happens, you will be notified that civilization has collapsed and, to rub salt in the wound, the planet reverts to the evolutionary timescale speed.
- Just how easy it is for the Nigh-Invulnerable robots to take over when even one is introduced. Unless you're intentionally trying to unleash them, seeing your carefully built up biosphere being wiped and cornered, robotic tiles becoming more and more common, can be fairly distressing.
- The Plague, particularly in the SNES version. Basically, it's represented by an animated skull-and-crossbones symbol with its jaw moving up and down. While creepy in and of itself, it's accompanied by a disturbing sound effect of distorted voices saying "No! No, no, no, no!"
- According to the SimEarth SNES instruction manual, Plagues are "not useful for anything but destruction".
- Porting Disaster: The Virtual Console port of the TurboGrafx-16 version works fine for the most part, but the Save-Game Limits due to the nonexistence of the file cabinet can be rather annoying.
- Uncanny Valley: Ironically, despite the MS-DOS version having the simplest graphics, it puts a realistic human face on Gaia rather than the cartoony eyes and mouth that the other versions opt for.
YMMV / SimEarth