Alternate costumes - Successfully complete the game to unlock a new costume for Asterix. Collect all the Gold Laurels in the indicated province to unlock the corresponding alternate costume:
Body Slam - Press Jump + Y to have Obelix do a body slam to the ground. Note: This will not affect Bosses.
Defeating The Norse Hammer - Pause the game during the battle with The Norse Hammer, then press B to advance past the fight.
Defeating the Battalion - Jump into the middle of the Battalion and repeatedly press A until they explode.
Defeating the Roman Spy - Repeatedly press A until he disappears.
Hit enemies with each other - Approach an enemy, hit them once, then press Y. Asterix will swing them around. Have Obelix throw an enemy towards you. If timed correctly, you can press Y and swing another enemy around, hitting the other enemy. A 10X modifier will appear.
Throw and hit enemies - Press L(2) to have Obelix to swing and throw an enemy to Asterix. Hit them before they touch the ground to instantly destroy them. Hit the enemy just after Obelix throws him (while they are in the air), and Asterix will glow and a 3X modifier will appear.