And UNDERTALE TEAM thanks you, the player, from the bottom of our hearts. Without you, all of this would be impossible.
Involvement in Story
Before the player starts the game, they name the first human and not the protagonist.
The duality of the protagonist and the fallen human is not revealed until the epilogue of the True Pacifist Route or (if slightly less clearly) the Genocide Route. Throughout the game, characters do not refer to the protagonist by name and instead call them "human" or "child."
The player often conducts the protagonist's actions, though some scenes relinquish control from the player. An example is when the protagonist hides behind the conveniently-shaped lamp, following Sans's instructions.
In the Genocide and True Pacifist routes, Flowey calls the protagonist by the player's chosen name. Flowey and Asriel are the only characters to do this; Asriel names his sibling in the True Lab VHS tapes and before his battle.
LV relates to the number of monsters killed, and higher levels of LV make it easier to harm others. Because LV and EXP display under the player's chosen name in the Stats menu, they increase the fallen human's ability to harm others.
At the end of the Genocide Route, the protagonist does not require a SOUL to attack. The player loses all control over the protagonist as they autokill Asgore and Flowey. The Bullet Board does not appear for either of these encounters.
Certain characters could be addressing the player in some scenes. For example, after the True Pacifist Ending Credits, Flowey appears and speaks into the fourth wall with no bullet board or ACT commands present.
Flowey begs for the world to be left alone and recognizes that the power to reset everything can still be used. However, this dialogue is up for interpretation because Flowey ends the conversation by addressing the fourth wall as the player's chosen name.
Another possible example is at the end of the Genocide Route when the fallen human speaks into the fourth wall. Again, this is up for interpretation as the fallen human uses "you" as opposed to a proper noun; they could be speaking to the protagonist.
One interpretation is that the place where the fallen human meets the player is in the protagonist's inner self, where the fallen human scares the player - the jumpscare only occurs if the player tries to resist their will.
- "Um... what... What IS your name? 'Frisk?' That's... A nice name." - Asriel
- "The more you kill, the easier it becomes to distance yourself. The more you distance yourself, the less you will hurt. The more easily you can bring yourself to hurt others." - Sans
- "Everyone will be ripped from this timeline... ...and sent back before all of this ever happened. Nobody will remember anything. You'll be able to do whatever you want. That power. I know that power. That's the power you were fighting to stop, wasn't it?" - Flowey
- "You've probably heard this a hundred times already, haven't you...? Well, that's all. See you later... <Name>." - Flowey
- "Greetings. I am <Name>. Thank you. Your power awakened me from death." - The fallen human