Mr.O Spawns at 7 notebooks unless your playing in free run mode. Currently, there is no way to stun him. May change in the future.
PNGling repellent is used on er when he emerges from the screens in the classrooms.
thank you. Also, I cleared the game with 42 characters ON! (This includes characters that are always on, such as Jack and Jaxxane.)
You can stun him with the Time Charm tho
