The Swapnote universe (いつの間に交換日記, Unnoticed Exchange Diary) is a messaging application for the Nintendo 3DS family.
Swapnote is the successor to the DS's Pictochat and was first launched on December 21st, 2011 in Japan through the Nintendo eShop. Similar to its predecessor, Swapnote allows players to send hand-drawn pictures to friends via StreetPass or SpotPass. As more pictures are sent, some perks are unlocked, such as the ability to draw messages in 3D; more perks could subsequently be unlocked using Play Coins. Pictures can be taken and edited on Swapnote, and audio can be added into pictures. When the user needs help, a Mii named Nikki would come and help with the problem.
On October 31st, 2013, Nintendo disabled Swapnote's SpotPass functionality; the reason for this is most likely because of Japanese children sharing Friend Codes with strangers who use Swapnote to send obscene photos.
In November 2016, the successor of Swapnote, called Swapdoodle was released, featuring Nikki in a new design.
Nikki appears as an Assist Trophy. When summoned, she uses her pencil to draw a picture, which attacks nearby opponents. She can draw a Bullet Bill, a flock of birds, a pinwheel, a dragon, a ghost, and even a destructible Smash Ball. She will draw up to 3 items before vanishing. She also appears as a spirit.