Beat Classic or Adventure mode with Mario, without continuing. Or, play Vs. mode 100 times. After meeting either requirement, Dr. Mario will appear as a new foe; beat him to unlock him.

In first stage of Adventure mode (The Mushroom Kingdom), pass the flagpole when the number of seconds on the timer ends with a "2." For example, 04:12 95. If your timing was true, Luigi will replace Mario in the next battle. Then go on and beat the rest of Adventure mode without continuing. Or, play Vs. mode 800 times. After meeting either requirement, Luigi will appear as a new foe; beat him to unlock him.

To unlock the stage based on Super Mario Bros. 2, collect the Birdo trophy. The Birdo trophy is one of the trophies that randomly appears in Classic, Adventure, and All Star modes. You can also win it from the trophy Lottery.

Hitting the Sandbag in the Home Run Contest 1,323 feet or more will unlock the classic Yoshi's Island stage from the N64 Super Smash Bros.

Giga Bowser is only found in Adventure mode. He's bigger than Bowser, and much more difficult to defeat! If you beat Adventure mode under 18 minutes, with Normal difficulty or higher, and without continuing, Giga Bowser will appear after you beat Bowser. Beat Giga Bowser without continuing to get the Giga Bowser trophy.

Get an 11-hit or higher combo in Training mode.

In the Event mode, clear event #14.

In the Home Run Contest, hit the Sandbag 1,485 feet or more.

Clear All-Star mode without continuing.

After you get the standard trophies for every character, you'll get the DK Jr. trophy. (Standard character trophies are earned by beating Classic mode, or by using a character 100 times in Vs. mode.)