How to Unlock Baby Luigi in Wii
- 1). Turn on the Wii console and insert the "Mario Kart" game.
- 2). Wait for the game to load and then select "Time Trials" from the list of game options. Choose "Expert" mode from the settings and select your desired character.
- 3). Select the first track and verify that "Time Trials" mode is active. If presented with the option to race the "ghost data" or "ghost racer," select "Yes" or "OK." When racing, you will see a semi-transparent character racing along with you. You need to beat this character in the first track to win the time trial.
- 4). Repeat step 3 with at least seven other tracks in "Time Trial" mode on "Expert" level. You must beat the "ghost" time on each of these tracks in order to unlock Baby Luigi as a usable character.
Source...