Normal mode: The default mode. In order: Snake, Castle Crasher, Salad Fingers, Weebl, Cuboy, Tankman, Fulp, Pico. Awards "Pico Day Massacre" Medal for 50 points.
Hell mode: Features more enemies between Fulp and Pico. In order after Fulp: Madness Dude, Snowball, Blockhead, Bob, Dad, Damian, Pico+Nene+Darnell. Awards "Nukedgrounds" Medal for 100 points.
F**KED UP mode: All enemies are active at the start. Awards nothing, other than bragging rights.