“The first time a Mii completes mission 20, game is over (with a “Mission Completed” message). Thereafter, however, 100 missions are available for progression.”

I recently played the game on a brand new Wii, and it took more than once of reaching mission 20 and of receiving the “Mission Completed” message to unlock the remaining levels. If memory serves, I think I had to beat mission 20 three times, before going onto mission 21 in the fourth.

The unlocking may have been related to medals being earned.

Can anyone substantiate this?