Warning: Spoilers Off applies to these pages. Please proceed at your own risk.

Examples from the second game:

Upon entering the cliff cave, Tralu's lair, you're greeted by a freakishly large spider. Arachnophobes beware.
The Dome of Slate test has you walking through a place where you can barely see where you are stepping on. If you fail and fall to the "ground" you'll be treated to Twinsen turning pitch-black and dying after struggling which looks like he fell into outer space. Nowhere else this can happen in the game.
Dr. Funfrock is already a nasty piece of work from the first game. How he amps up his game? By throwing children into lava just to spite Twinsen.
The last part of the game is full of these. After the Emperor starts the Emerald Moon engine you'll periodically see the moon ominously heading towards Twinsun, sometimes showing the moon very close to the planet. Should you get a game over you'll see in full the terrifying results of it crashing into Twinsen's planet.