Monoko is a character in the White Desert. She appears to be a young, rather depressed-looking black and white girl.
This unassuming appearance only remains until you use the Stoplight effect or her. She immediately stops moving and changes into what seems to be her true form, which is still recognizable, but horrifically changed: She now has five arms, one of which sprouts out of the top of her head; her stomach grows what seems to be a bloodless wound or vortex; and her right eye and mouth begin to melt or dribble. This is usually interpreted as her being crying and drooling.
If you run into Monoko while she is in this form, the screen changes to black with a detailed, non-sprite Monoko bouncing in random directions. Kalimba music plays.