Complete the game to unlock New Game + mode. In this mode, you can start a new game and keep your Roses and Weapons from the previous game.
Unlock the following dresses to gain their effects by completing the corresponding chapters:
DRESS - EFFECT - CHAPTER
Steamdress: Hatter's Domain - When equipped breakables drop more teeth and roses. - Chapter 1
Siren: Deluded Depths - When equipped your enemies drop twice as many roses. - Chapter 2
Silk Maiden: Oriental Grove - When equipped your enemies drop twice as many teeth. - Chapter 3
Royal Suit: Queensland - When equipped your health is limited to four roses total. - Chapter 4
Misstitched: The Dollhouse - When equipped your Shrink Sense duration is doubled (Chapter 5
Classic: Infernal Train - When equipped you will regain health when shrunk - Chapter 6
Psychonauts easter egg:
In Chapter 4, after doing the first chess puzzle, you will be chased into a hole by the giant unbeatable card monster. When you first arrive down there, go a short distance ahead and look at the right wall to find a heart stone. Shrink down to discover that it is a fake rock. Run into the keyhole tunnel and on the other side will be a floor where you can use a bomb to break. Do so, then go down the stairs to get a memory and extra teeth. Notice the skeleton sitting on the chair--it is Raz from Psychonauts. He can be identified by the red goggles, his shape, and the position that he is in (which is the stance he uses for a mind attack). It kind of looks like Raz is dead, perhaps signaling that there'll be no Psychonauts 2.
"Level-Headed" achievement hint:
After completing the game, select the final chapter and go directly to the Boss battle. Defeat the boss without using hysteria to unlock the achievement.
ACHIEVEMENT - HOW TO UNLOCK
Everything fit to remember (30 points) - Find all Memories.
Nothing Like the Smell of Bacon (10 points) - Pepper All Snouts in a Chapter.
Seasoned Campaigner (30 points) - Pepper All Snouts in the Game.
Shooting the Moon (10 points) - Collect 4 Jars of Rose Paint.
Painting the Town Red (30 points) - Complete all Radula Rooms.
Family memories fond and faded (10 points) - Find all Liddell Memories.
The Persistent Flourish (75 points) - Complete the Game on Hard Difficulty.
The Beginning of the End (20 points) - Complete Chapter 1 on Nightmare Difficulty.
Madness Prevails (80 points) - Complete the Game on Nightmare Difficulty.
The End of Daze (10 points) - Complete Wonderland Chapter 5.
The Strong Survive (25 points) - Complete the Game on Easy Difficulty.
The Imaginative Endure (50 points) - Complete the Game on Normal Difficulty.
No quarter! No mercy! (20 points) - Defeat 100 Ruin Enemies.
52 Pick-Up (20 points) - Defeat 52 Card Guards.
Calm In the Face of Death (30 points) - While on your last Rose, kill 5 Enemies without activating Hysteria.
Beware of the Lagomorph (20 points) - Kill 30 enemies with the Clockwork Bomb.
Cold Arms, Cold Heart (30 points) - Defeat the Drowned Sailor without taking any damage.
Pulling Strings (30 points) - Defeat the Dollmaker without taking any damage..
Dead Hatter (10 points) - In American McGee’s Alice, Complete Behind the Looking Glass.
Royal Approach (10 points) - In American McGee’s Alice, Complete Queen of Heartsland.
Full Recovery (50 points) - In American McGee’s Alice, Complete the Game.
Madness Begins (10 points) - In American McGee’s Alice, Complete Village of the Doomed.
Skool-Leaver (10 points) - In American McGee’s Alice, Complete Fortress of Doors.
Out of the Woods (10 points) - In American McGee’s Alice, Complete Wonderland Woods.
Brollyant (20 points) - Kill 10 Bitch Babies with Deflection.
That's Using Your Head (20 points) - Complete Off With Her Head Part 2 in under 6 minutes.
Dress-Ups (10 points) - Equip a Different Domain Dress .
Weapon Schizo (10 points) - Hobby Horse to Vorpal Blade to Hobby Horse Combo.
Ship of Fools (20 points) - Complete HMS Gryphon without taking Damage.
Just peachy (20 points) - Collect all Peaches in the Scroll of Destiny.
Grandmaster (10 points) - Complete a Chess Puzzle without failing.
Venting frustration (10 points) - Spend 7 minutes on steam vents.
Level-Headed (50 points) - Finish the game using Hysteria only once.
Eyes on the Size (10 points) - Find the hidden Shrink Sense Decal.
Grind 'em All! (10 points) - Kill 5 Bolterflies in a row with the Pepper Grinder.
Tea Party (10 points) - Destroy 10 Ruin Barriers.
Strike a Deal (10 points) - Upgrade a Weapon.
More than a Mouthful (20 points) - Fully upgrade a weapon.
Armed to the Teeth (30 points) - Fully upgrade all weapons.
Ground Pork (10 points) - Acquire the Pepper Grinder.
Strange Hobby (10 points) - Acquire the Hobby Horse.
Death by Darjeeling (10 points) - Acquire the Teapot Cannon.
Snicker-snack! (10 points) - Acquire the Vorpal Blade.
Grim Folly (10 points) - Complete Wonderland Chapter 2.
When Worlds Collide (10 points) - Complete Wonderland Chapter 3.
The Harder They Fall (10 points) - Complete Wonderland Chapter 4.
No Happy Returns (10 points) - Back to Wonderland.
End of Innocence (10 points) - Complete Vale of Tears.
Hatter's Demise (10 points) - Complete Wonderland Chapter 1.
Neighslayer (10 points) - Hit 4 Enemies With a Single Hobby Horse Ground Smash