There was an update to the 3DS last week which added a few features (like 3D video recording and marginally better friend list management), and as part of it there was a new Streetpass Quest II “mission” for the Mii Plaza. Hurrah!
Unfortunately, you can’t do it unless you’ve completed the first Quest twice, when I’d only done it once. So, armed with 300 play coins, I set about doing it again. Surprisingly, I managed it with “just” 240 coins used, mainly because I had a White Cat exactly when I needed one, whereas before I wasted 100+ coins waiting for one. I also had a decent strategy too, using a Purple Cat (when I had one) first to poison the enemies the maximum number of times (one for each Hero), then Orange next (if possible) to add an extra attack to each of the remaining 8 Heroes, and finally using magic on any armoured ghost when my Heroes were only Level 1.
I also got lucky with some Green magic attacks – managed to wipe a load of HP off some of the ghosts (including the final one!) while they were napping. Ace.
Now I have all the original hats! Hurrah!