Bonus comic - Collect all the artwork to unlock a secret comic at the inventory screen.

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Stray Cat (5 points): Have T. Kemper join the player as a support character.
All Together Now (5 points): Do a 3-member Team-Up Attack.
A Winner Is You (10 points): Successfully complete the first episode.
Nine Lives (15 points): Kill an enemy using T. Kemper's basic attack.
Pack Rat (15 points): Find and collect all of the hidden collectibles scattered around the game.
Steel Devils (15 points): Explore the world to find all the robots, and defeat them all in combat.
Pacifist (15 points): Only use counterattacks, health items, or distraction items to win one battle.
Silent, But Deadly (30 points): Fight, and destroy the final Boss without using any healing items.
Immortal (20 points): Play and win the game without allowing a character to die during combat.
Fight 'Em With Items (20 points): Find and use every item in the game at least once.
Level Awesome (20 points): Kill enough enemies in the game to get the XP necessary to get all party members to Level 15.
Clean Sweep (30 points): Find and kill every possible enemy in the game.