Galacta Knight did not originate from fanon, and more information can be found on their respective wiki(s). You may read more about it on the following wiki(s):

Galacta Knight Dreamland Wii U

Galacta Knight is a character from the Kirby series. Galacta Knight first debuted in the Nintendo DS remake of the popular Super Nintendo Entertainment System title Kirby Super Star Ultra, where he served as the final boss of the "Meta Knightmare Ultra" sub-game.

He is introduced once Meta Knight summons the character of Nova, who grants him a single wish. Meta Knight's wish is to fight the greatest warrior in the galaxy, and Nova summons Galacta Knight, who was said to have been sealed away due to his immense power.

He also makes appearances in the Super Star Ultra sub-game "The True Arena", where he served as the penultimate boss. He also appears in Kirby's Return to Dream Land, once more as an opponent in "The True Arena" mode, this time being fought on the thirteenth stage.