The source of the Internet slang screw is Ragnaros, the Firelord in "Hearthstone"
This meme is a homophonic meme, taken from the last two words at the end of the name of the follower, named screw.
Because its effect is to cause 8 points of damage to a random enemy at the end of the player's turn, cards with similar effects are also named various screws.
The small screw refers to the siege engine
The light screw refers to Ragnaros, the lord of glory
The small light screw refers to the enthusiastic bartender /Sandhoof water mover.