During the bounce up during a game, hold Up + Select + X, then release Select, Up, X (in that order). Replace X with Triangle, Circle, or Square for different cheats.
At the main menu, press Start, then hold every other button at the same time. A new screen will appear, where you can select the team and then the player that you wish to have his name changed.
Select Brisbane at the Gabba against any other team on the easy difficulty setting and you will be unbeatable.
If a player has retired during the last season, there are 10 or more reserves you can put in to replace the retired players(s).