To increase hitting power, insert "triplecrown" at the cheat code menu. If done correctly, the heart of your lineup (3rd, 4th, and 5th batters) will have increased hitting (50%). This will last for one game only.
To increase your team’s power for a single inning by 25%, put “mightymick” (minus the quotes) into the cheat code menu.
To unlock Mickey Mantle in free agency, enter “themick” in the cheat code menu.