When you first look at the XBL Achievements for the game, there are six "secret" achievements to unlock. Here they are, and how to obtain them:

Let The Creative Juices Flow (5pts): Create one original Superstar using the Create-A-Superstar mode.
Crown Us The Champ! (10pts): Create a Tag Team Championship in Create-A-Championship mode.
Mr. PPV (5pts): Create an original PPV event in Create-A-PPV mode.
With Friends Like These (5pts): Create an original stable of Superstars in Create-A-Stable mode.
Self Anointed Champion (10pts): Create a singles Championship in Create-A-Championship mode.
Curtain Call (5pts): Create an original entrance in Create-An-Entrance mode.

Submitted by paulackerman