UNDERTALE/Frisk

Overview
Frisk is the main character of Undertale and among the most speculated-about. Their gender is unknown, so are any emotions they feel, but they are said to be full of DETERMINATION. The only thing established for sure about them is that they climbed a mountain that people are rumoured to disappear on, bearing nothing but a stick and a bandage, for an unknown reason.

Appearance
Frisk looks strangely like Chara, in the way that they both have the same outfit and hair. Frisk, however, has a stoic expression that looks like this (-_-), while Chara is smiling the whole time they appear on the screen. Frisk also has the colors blue and purple for their shirt colors, while Chara has the color negatives of that, lime and blond.

Personality
While never seen having emotions, their personality becomes like Chara's in the Genocide Route, wanting to kill monsters before they can escape. Other than that, you can make Frisk say and feel whatever you want.

Pacifist Route
Just don't kill any monster, just spare them. Frisk doesn't really change much throughout this route. Oddly enough, this is the only route in which the name Frisk is even used by another character. All other routes... nothing.

Neutral Route
Frisk doesn't change much here either.

Genocide Route
On this route, in the WATERFALL area, Frisk becomes possessed by Chara and encounters become marked by Chara's smile. From then on, until you abort the Genocide Route, all encounters are marked with that creepy smile.

Trivia

 * Frisk is the 8th human to fall down into the underground.
 * Chara was the first, but their SOUL disappeared before Asgore could use it.
 * All the perished fallen humans left their items behind. You can pick most of them up on the Genocide Route for free, buy them on the Neutral and Pacifist Routes, or you can ignore those items entirely until you find the Worn Dagger and Heart Locket.
 * Frisk and Chara are similar in a lot of ways, and may be considered adoptive siblings depending on one's choices throughout the game.
 * The game only allows you to name one character; while it sets things up to look like Frisk is the one being named, it is revealed across various endings that the fallen child being named is actually Chara; Frisk's name is immutable.