There's a good chance these are fake. However, one guy who did an IXS text walkthrough said he was able to get one of them to work, so it's questionable. I have yet to test them, but I'll post them here anyways:

Cheat Mode
Press the following actions to activate cheat mode: Up, Down, Up, Up, Jump, Pizza, Jump, Jump, Down, Up, Down, Down, Pizza, Jump, Pizza, Pizza, Up, Down, Up, Up, Jump, Pizza, Jump, Jump, Down, Up, Down, Down, Pizza, Jump, Pizza, Pizza.

Display Cheat Mode
Cheat Mode must be activated first for this code to work. Press the following actions during gameplay: Up, Down, Up, Up, Left, Right, Left, Left, Down, Up, Down, Down, Right, Left, Right, Right.

Get All Mini-Games
Cheat Mode must be enabled for this code to work. Press the following actions during gameplay: Up, Down, Up, Up, Jump, Pizza, Jump, Jump, Down, Up, Down, Down, Right, Left, Right, Right.

Skip the Current Level
Cheat Mode must be enabled for this code to work. Press the following actions during gameplay: Up, Down, Up, Up, Jump, Pizza, Jump, Jump, Left, Right, Left, Left, Jump, Pizza, Jump, Jump.

When you do test them, be sure to record and upload to Youtube.

When you do the display cheat mode, stars come from Peppers head and a sound plays (the sound from when you get a red brick), however the rest do nothing.