Foreshadowing: Before Swapdoodle - the successor to Swapnote - became a thing, there were way too many badges of its mascot Nikki in the arcade that had no official source. Turns out Swapdoodle is where the art originated from.
I have not found confirmation that this is the case, so I commented this out. If one has proof, please provide.
It could be simply that people liked Nikki so they made badges for her. This is the case with Ashley from Wario Ware, in Japan she also has "too many" badges, this is due to her popularity. Also note Nikki has a Club Nintendo Japan exclusive quiz game and was something of a mascot for a while on Nintendo Japan's news page.
I have not found confirmation that this is the case, so I commented this out. If one has proof, please provide.
It could be simply that people liked Nikki so they made badges for her. This is the case with Ashley from Wario Ware, in Japan she also has "too many" badges, this is due to her popularity. Also note Nikki has a Club Nintendo Japan exclusive quiz game and was something of a mascot for a while on Nintendo Japan's news page.