This was probably asked a lot already, but is/was there anything similar to pictochat but for a 3ds?
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Swapnote/Swapdoodle. But you can also install pictochat!
Swapnote and Swapdoodle are the apps made for 3DS, but there is also a way to install the original Pictochat from the DSi on your 3DS and it actually works :)