Fanatic Blues appear only in Solarise after you beat the game once.
They can randomly appear in said level, but not in the tutorial. They are the remaining forces of Big Blue who still believe that their leader is still alive after their previous defeat on their moon base, which resulted in the loss of some, if not most, of their other comrades.
The Fanatic Blues seem to believe that, even if Big Blue were dead (though he is technically still alive as a normal stick person again), his "ways and teachings" still live on through them, creating a legacy of the now defeated leader of the menace that threatened the Slush Fighters at the beginning.
The Fanatic Blues uses their blue brush to place in one block in a random place, one after another.
After 3 seconds has passed from placing a block, they will place another one, constantly. Other than that, the Fanatic Blues are not much of a threat.
"You cannot break the will of the Blues!" - In-game determined dialogue.
"Big Blue lives on through us!" - In-game determined dialogue.
- They are one of the new forces and types of Blues encountered in Slush Tile Rush, the others being Armoured Blue, Moon-Bleached Blunatic and the Blue Fairy.
- The Fanatic Blues seem to be unaware that Big Blue is indeed still alive, only "cured" from the corrupting abilities of the Blue Paint.
- They are actually a bit more purple than blue.