Aquadome:
Hit a homerun into the pool at Steele Stadium, into the swamp at Gator Flats, and 
into the lake at Frasier Field. The Aquadome stadium should now be unlocked. 

Abner Dubbleplay:
Earn all twenty certificates to unlock Abner Dubbleplay as a player.

Barry Deejay:
Have a saved game file from Backyard Basketball on your memory card.

Derek Jeter:
Execute two double plays in a single game in season mode.

Greg Maddux:
Win 20 games in season mode. Note: Try playing a 32 game season.

Mike Piazza:
Hit a grand slam in season mode.

Mr Clanky:
Complete Clanky's Coaching Box.

Pedro Martinez:
Throw a shutout in season mode.

Randy Johnson:
Get 75 career strikeouts, which includes the playoffs. If you have any other 
pitcher, put him in. He does not have that good Running, Contact or Defense 
status, but is a very good pitcher. 

Shawn Green:
Hit the ball to gain a base 60 times in season mode. 

Certificate list:
The certificates required to unlock Abner Dubbleplay are as follows:

3 Homerun Game
Grand Slam
Hit The Cycle
10 Strikeout Game
3 Stolen Base Game
Winning Pitcher
Threw A No Hitter
Threw A Shutout
5 RBI Game
MVP Of Game
10 Career Hits
30 Career Hits
80 Career Hits
5 Career Homeruns
15 Career Homeruns
30 Career Homeruns
25 Strikeouts
75 Strikeouts
150 Strikeouts
10 Pitching Wins
20 Pitching Wins
30 Pitching Wins
10 Stolen Bases
25 Stolen Bases
50 Stolen Bases 

Better performance:
Put Amir Khan and Achmed Khan on the same team and both of their skills will 
increase. The same happens when Ashley Webber and Sidney Webber are on the 
same team. 

Major league players will have increased skills when playing for their real life 
team. For example, Randy Johnson will perform better when playing as an Arizona 
Diamondback. 

Better bats:
To get a special bat (in any mode except tee-ball) you must get a double play. You 
can walk a man. When the other player comes up, he might hit a single. Note: Get 
a fast pitcher to run to first and tag the player out. Note: Sometimes you may 
strike out the person or not get him if you have two outs. 

Home Run Derby:
Note: You have to be fast. Choose two people and select a third person 
immediately before the screen changes. This will help you get more hits and home 
runs.