In the cafeteria of Queen Zenobia, there's a soda vending machine with a brand named "Trish". This is likely a reference to Trish, a character from the Devil May Cry series.
Clive R. O'Brian and Parker Luciani both give out some extra dialogue if the player tries to scan them with the Genesis Scanner. No other character in the game reacts this way.
You can see HUNK in the original trailer for the 3DS, even though he didn't appear until the HD version where he is an unlockable character.