KFC

KFC is the familyship between Kris from the Deltarune fandom and Frisk and Chara from the Undertale fandom.

Canon
The characters have not interacted as Kris only appears in Deltarune while Frisk and Chara appear in Undertale. Kris seems to be the Deltarune counterpart of both Frisk and Chara. Similarities included:
 * All three are humans.
 * All three have the red SOUL, speculated to represent determination.
 * All three have similar haircuts.
 * None of the three have a determined gender.
 * Kris is a playable character like Frisk.
 * Kris' name is one letter away from being an anagram of Frisk.
 * In the Light Realm, Kris has the same skin and hair color as Frisk.
 * Kris wears a green/yellow shirt similarly to Chara.
 * Like Chara, Kris was adopted by the Dreemurrs.

Fanon
Following the release of Deltarune, fanart of this trio started to be made as Kris had similar traits to both Frisk and Chara. In fanart, Kris is often portrayed as the older sibling of Frisk and Chara. This familyship can be seen as an expansion to a family version of Charisk, where Chara and Frisk are portrayed as siblings.

The name KFC for the ship comes from the first letters of each character. One of the earliest known uses of the name KFC for the characters is in a Drawception game where AngieFox02 wrote their first letters in that exact order and people in the comments started pointing it out. DeviantArt user Kaitogirl has made fanart of the three at KFC.

On AO3, this exact trio is not an existing tag yet, but non-romantic ships between Kris and both Frisk and Chara (without the third) and a non-romantic ship between the three and Asriel exist.

Fandom
DEVIANTART