These unlockable stages will replace the ? marks on the Story menu.
When you complete every game in the spindex, you unlock WarioWare Twisted in the games section of souveniers. The game restarts to the GBA load screen, but the load screen looks different.
Once you complete Warioman you will unlock the Minigame Towers. I dont know if there is a boss tower.
Get a high score on every microgame through 'Zukan' mode
Complete a character's stage
Complete Wario's Final Stage
Complete every single microgame at least once