Go to create a champ, use first or last name as GETFAB and save. Go to Play Now or Hard Hits. Fabolous is now unlocked as a heavyweight.
In the bonus game Super Punch-Out, complete all of the four circuits. Then, go back to Fight Night: Round 2, select Play Now, and then Heavyweight. You'll now find Little Mac in the selection of boxers
Unlock all venues
go to Game Modes screen, tap left 16 times. You will hear a sound effect like a bell and you've now unlocked all venues.