Fleg, Gleeb, and Spork are the two most prominent antagonists in the Goosebumps book The Beast From The East.
When the three protagonists, Ginger and her twin brothers Pat and Nat, get lost in an odd part of the woods, they encounter Fleg, Spork, and a large group of other large bear/beaver creatures playing a version of tag called "Beast from the East". The penalty for being "Beast from the East" (aka "It") after sundown is getting eaten.
Ginger manages to tag Spork, but is tagged back just before the end of the game. Just as she and her brothers are about to become dinner, the beasts notice that Pat and Nat are identical and claim that they have performed a "classic clone" move, apparently not grasping the concept of what twins are. Fleg lets the siblings go, believing them to be expert players.