PS135 is a Mario Sprite being controlled by the Power Up State 135, using Mario's normal look to lure in prey to kill and eat for sustenance, using the forest of illusion as a home of sorts.
He also tortures the residence of Dinosaur Land including Oogtar, Yoshi, and many other residents in Dinosaur Land.
Once entering the general area of Dinosaur Land it's extremely hard to get out of Dinosaur Land without trying to make a deal with the Mario look-a-like. PS135 is afraid of uncle grandpa.