Press Plus when you are about to lose a fight in Career mode. Select "Restart" and you will not be marked with a loss, and have the benefit of seeing your opponent's moves and weaknesses.
Champions mode
Win ten bouts in Mac's Last Stand.
Character audio
Complete all three challenges in Exhibition mode to unlock your character's audio gallery.
Donkey Kong in Exhibition mode
Defeat Donkey Kong in Last Stand mode.
Gallery introductions
View a boxer's introduction to unlock it for replay in the gallery.
Headgear
Lose 100 times total in single player mode to unlock the headgear, which provides invincibility.
Hidden Mini-Game During Contendor Credits
After you have finished Condendor Career or have viewed it under "Options," you will notice that you can still use your cursor and you will notice a score display at the top of the screne. The object is to correct the misspelled names of the developers and to remove the names of your oppenents. Be on the lookout for a letter of a developer's name to look different then it should. Click on the name and it will turn green and be corrected. Be careful not to click it again or hit one that is already correct since you won't get points for the correction. If you click on one of your opponent's names they go by, they will vanish from the scene.
Last Stand mode
Defeat Mr. Sandman in Title Defense mode.
Major Circuit
Win the Minor Circuit Championship Title.
Messing with Mac
On the main menu (after you have chosen a profile), there are five different ways to interact with Mac.
Hover your pointer around his right foot and he'll try to stomp on it
Hover about his left foot and he'll jump
Point at his left hand and he'll punch at you
Point at his face and he'll try to swat you away
Spin the pointer in circles around his face and he'll become dizzy!
Note: These only work while Mac's standing still, he won't react if you try to touch him while he's moving.
Recover from TKO
If you are TKO'd and the ending animation begins, quickly tap 1 and 2 repeatedly (Wiimote controls). If done correctly you will get one more chance. Note: This can only be done once per fight.
Regain health
Rapidly tap Plus and Minus alternately between rounds until a chime is heard. Your health will increase at the start of the next round.
After knocking down your opponent, rapidly tap Plus and Minus alternately. Mac will pump himself up and regain some energy while the opponent is down.
Press Minus during the dialogue between rounds. Doc will use a Remedy Bar and Mac will regain some energy. This can only be done once per opponent.
Title Defense mode
Complete the Minor, Major and World Circuits. In this mode you will be challenged by all of the fighters previously fought, but with different patterns and strategies.
Weasel the Opponent's Energy
Want to go for a quick TKO in the next round? Work the opponent's energy bar to nearly zero and let the current round's timer expire. On the next round, they usually start with the life you last left them with. Throw them down, and you should have most of the next round to KO them two more times for an easier TKO.