If you viewed my last post that was only japanease version so the real way to unlock him is here (NOTE action replay is required)
1. go to test map 2 with all 150 stars to get 151 stars
2. Blast into the black box using "View black box hack"
3. then blast into the peach picture
4. you get teleported to a level
5. complete the level and beat the boss "
waluigi himself 6. When you defeat him he runs off and you complete the level
7. go to the character select room the ice bully boss will be infront of the white door...
8. chase him like a bunny and then when you catch him he will give you a upside down L key
9. go in the white door and you become waluigi! go to the front of the castle ITS FLOODED swim up to the top right corner and press Y it calls down lightning then rips a hole in the roof go in theres no water there...
10. activate the button and then watch the cut scene then jump out of the hole and everything is back to normal.
(NOTE the black box on the character select screen is gone)
Have fun with
waluigi! You don't learn from success you learn from failure