Character Costumes
You can get more character costumes by playing with the same character for five missions in Dance Master mode. Once you do this, that character will have additional costumes in the shop that you can buy with points.
Mission C-21
To unlock mission C-21, you have to do less than 100 perfects on mission C-18.
Mission C-27
Mission C-27 is attained by achieving 36,000,000 or more on mission X-21.
Mission D-44
Get a max combo of 1,000 on mission X-30 to get to mission D-44.
Mission D-45
D-45 is unlocked by getting 50 on mission X-31.
Mission D-47
By achieving 35,000,000 points on mission D-43, you can unlock mission D-47.
Mission E-9
Mission E-9 is possible by getting less than 8,600,000 on mission E-6.
Mission X-1
A rank of AA or better on mission A-5 unlocks mission X-1.
Mission X-2
Get a rank of AAA on mission A-6 to unlock mission X-2.
Mission X-3
Achieving a rank of A or higher on mission B6 gets you to mission X-3.
Mission X-5
With less than five greats on mission X-3, you'll get mission X-5.
Last Mission for Dance Master Mode
To play the last mission and complete Dance Master mode, clear areas A, B, C, D and E by playing the three special missions in each area.