When you realize that Frisk is actually Chara; When you finally beat Sans after dying 158 times; When you see someone killing all the innocent monsters; When you find a new secret room in Waterfall; When you spare all the enemies and get the Pacifist ending; When you try to flirt with someone but they friendzone you; When you hear the iconic 'Megalovania' track; When you accidentally kill Toriel on your first playthrough; When you encounter Flowey and he starts trolling you; When you realize that Alphys has been spying on you; When you come across a funny pun in the game; When you try to solve one of Papyrus' puzzles; When you defeat Asgore and prepare to face Flowey; When you encounter the Annoying Dog throughout the game; When you find out that Sans is the final boss of the Genocide route; When you encounter the Temmie Village for the first time; When you encounter Mettaton's fabulous transformations; When you meet Asriel and learn about his tragic story; When you see Toriel's reaction to your choice in the Ruins