This YouTuber had a corrupted SD card on his Nintendo 3DS. You'll never believe what happened next.
In fixing his saves, he discovered a way to infinitely respawn special StreetPass visitors. This means, as he astutely notes, that Nintendo 3DS users who live in very rural areas (raises hand) can finally complete a Puzzle Swap puzzle in less than two years.
The 10-minute video above gives a full explanation (with some ... unusual voice-recognition subtitles), but it works this way, per YouTube's Anthony Schwader.
1. Use the special guest in all of the StreetPass mini-games [Find Mii 1 & 2, Puzzle Swap, etc.]
2. Select SETTINGS and deactivate STREETPASS (This also deactivates SPOTPASS)
3. DELETE the special guest from your plaza
4. Hit HOME and exit StreetPass Mii Plaza
5. Re-enter StreetPass Mii Plaza
6. Select SETTINGS and reactivate STREETPASS
7. Reactivate SPOTPASS next
8. Wait for the beautiful BLUE NOTIFICATION
9. Hit the HOME button and the NOTIFICATIONS bubble should pop out.
10. Enter NOTIFICATIONS menu and select LAUNCH SOFTWARE at the bottom
11. SP Mii Plaza will close and re-open by itself and the special guest should come strolling through to greet you like it was the first time ever!
Schwader demonstrates it with Abraham Lincoln, a special guest Mii rolled out for Friday's launch of Code Name STEAM., but it should work with any special guest Mii.
I live in a small town, and barely get any StreetPass even when I go to the Walmart — though I did get a visitor once when I went to the fire hall to vote in 2012. It was awesome. So this will definitely come in handy for beating Find Mii 2. It sure beats walking.