Nekoamon is a horrorbrew created by VertederoGM. He is the main antagonist of the April Fools' Day version of Mario 85, that takes place in Syobon Action. Nekoamon appears as a large, dark cat figure outlined in white lines, with two white dots and a wide smile. He can also change his main color (white) to red, mainly to intimiate people. Nekoamon has a similar personality to MX, however, he seems more aggressive and cunning, creating traps out of pipes to ruin the taste of victory. Nekoamon is an entity found in Syobon Action, who has turned the game into his domain, where he has lured an eight-year-old boy named Lucas. Like MX, Nekoamon chases the player around the level, breaking through blocks. At one point, Nekoamon uses a Warp Pipe to lure the player into an ambush, and later, he discards the Warp Pipe the player was attempting to enter and crashes through the ground. Nekoamon stops near the end of the chase, and falls from the sky at the end of the level to crash through the ground moments before the player can escape through another Warp Pipe. Nekoamon also appears in the ending screen, depicted playing the game with the player character.

More facts here: https://house-of-horrorbrews.fandom.com/wiki/Nekoamon