The good route of Undertale, most commonly referred to as the Pacifist Route, is the one in which the player resolves each monster encounter without taking a single life, thus winning the trust of the Underground and, ultimately, allowing them to migrate freely back to the surface to start a new life. Along the way, you end up hanging out with each of the main monster characters, getting to know their personalities and backstories.

Tropes appearing specifically in Undertale's Pacifist Route include:
  • Bitch in Sheep's Clothing: Yes, it is possible to complete the Pacifist Route while generally being a dick to everyone; as long as you don't kill anyone (or leave them for dead, in the case of Undyne), you can be as horrible as you like. Surprisingly, Sans the Skeleton won't call you out on your douchebaggery.
    • That being said, there are two minor characters that will call you out in the Pacifist Ending sequence.
      • If you simply stood around without doing anything while Monster Kid was hanging for dear life from a bridge, they'll remember how you just sat around and watched them almost die. If you try talking to them, they'll stammer for a bit, before quickly telling you not to talk to them, and remain mute afterward.
      • If you had previously eaten the Snowman Piece in front of the talking snowman, he'll have some harsh words for you:

"Ah, the barrier's open...? You know I cannot move. Why are you telling me? To mock me? Everyone may think you are a good person, but this snowman knows the truth. Someday, your friends will realize your heart is as cold as my butt."