Parody Mode: 
Beat the game once, and when you go play it again, your characters will have different voices. 

DVD Secrets: 
Go to the Extras menu of the DVD (that's included with the game) for secrets that relate to the game.

Defeating Goblins: 
Use Wood magic, two shots should kill them. 

Hidden Keywords:
Keywords can be found everywhere, here are the keywords found on the Sigma server: 

Keyword: 
Secret item received from gott's statue 

Noisy, Sacred, Ringing Ears: 3-Floor Tower (trade to Alicia for Cat's Hat) 
Unusual, Ghostly, Remnant: Doll Amulet (trade to Stare for Cat's Armor) 
Barking, Hot-Blooded, 500 Lohan: Magnolia Miso (trade to Flare for Cat's Gloves) 
Ancient, Destroyer's, Battlefield: Scent of Gero (trade to Fool for Cat's Boots) 
Greedy, Gambler's, Drift: Boxed Lunch (trade to Benoit for Yoshida) 
Tested, Morphean, Alchemy: Field's Deed (trade to Waffle for Dreams of Yore) 
Entwined, Prejudiced, Chaos: Rouge Fragment (trade to Cyan for Gimme Life) 
Abrasive, False, Tragedy: Maiden's Plot (trade to Teria for Thunder Dad) 

Keyword: 
Secret item in chest 

Noisy, Sacred, Ringing Ears: Lady's Cap 
Unusual, Ghostly, Remnant: Lady's Mail 
Barking, Hot-Blooded, 500 Lohan: Lady's Gloves 
Ancient, Destroyer's, Battlefield: Lady's Shoes 
Greedy, Gambler's, Drift: Lady Killers 
Tested, Morphean, Alchemy: Vampire Blade 
Entwined, Prejudiced, Chaos: Kokoro 
Abrasive, False, Tragedy: Bear's Sword and Crystal Stone