Calyrex 

Calyrex is originally a Pokemon introduced in the Crown Tundra expansion of Pokemon Sword and Shield. Due to it being a "king" Pokemon and yet being a very weak Pokemon, it is used to describe a person trying to flex even without the required knowledge to flex.

That person is such a Calyrex, he tells everyone how to draw this artwork and yet he could not draw it himself!

Calyrex by StartWithSobble November 6, 2020