The Blue Slime is an enemy that makes a brief appearance in the first season episode, Reality 2.0. It comes out of a virtual Slushie machine in Bosco's store. It is a parody of the Slime enemies in the real-world game Dragon Quest. The Blue Slime is defeated by using the Wooden Long Sword of Extreme Longness (obtained from Bosco for five Gold Coins) in an rpg-like battle. This reduces it to a puddle of "slime slime" that can be used to get the +2 Sword unstuck later on.
While easily defeated, the Blue Slime respawns as often as the player has any interest in fighting it.