There are 18 Secret Eggs to be found in the game, one for each level of the 
game. Whenever you find a secret egg, it will unlock one of the following items. 
And the unlockables are unlocked in the following order, regardless of which egg 
you've found first.

Effect - Code
--------------------------
Advertisement for the books "Eragon" & "Eldest" - Find Secret Egg # 01 
Bonus Level: Throne Room - Find Secret Egg # 18 
Commentary - Art Direction - Find Secret Egg # 04 
Commentary - Birth of a Game - Find Secret Egg # 05 
Commentary - Design - Find Secret Egg # 03 
Commentary - Edward John Speleers - Find Secret Egg # 02 
Commentary - Evolution of Games - Find Secret Egg # 16 
Commentary - Garrett Hedlund - Find Secret Egg # 15 
Commentary - Orchestra - Find Secret Egg # 07 
Commentary - Robert Carlyle - Find Secret Egg # 13 
Commentary - Saphira - Find Secret Egg # 08 
Commentary - Sienna Guillory - Find Secret Egg # 09 
Commentary - Sound Effects - Find Secret Egg # 14 
Concept Art - Beor & Varden - Find Secret Egg # 17 
Concept Art - Characters - Find Secret Egg # 10 
Concept Art - Gil�ead - Find Secret Egg # 11 
Concept Art - Spine, Carvahall & Daret - Find Secret Egg # 06 
More Concept Art - Find Secret Egg # 12