Unlock the following options at the "Top Secret" menu by performing the corresponding tasks:

OPTION - HOW TO UNLOCK
Additional Character Profiles - Solve all 168 puzzles.
Character Profiles - Collect 4,200 Picarats
Character Voices - Collect 5,000 Picarats
Game Music - Collect 4,700 Picarats
Movies - Collect 5,200 Picarats
Story Art - Collect 4,500 Picarats

Unlock the following Layton Challenge puzzles in the "Bonuses" menu by performing the corresponding tasks:

CHALLENGE PUZZLE - HOW TO UNLOCK
The Hotelier's House - Complete all ten toy car courses.
The Messenger's House - Complete all twelve parrot delivery errands.
The Storyteller's House - Complete all three picture books.
The Time Traveler's House - Complete the game.
The Puzzle Keeper's House - Complete 165 puzzles.

Complete Professor Layton And The Diabolical Box to receive a system-specific code. Enter the "Top Secret" screen in Professor Layton And The Unwound Future and choose the "Hidden Door" option, then enter the code.