this is called the memorex universal game selector. it’s compatible with the ds lite, dsi, and 3ds. ive had it for 7 minutes and im in love.
you plug this beauty into the back where you’d normally put a game
load it with up to 3 games you want to have with you or whatever
SLIDE THIS THING ON THE BACK
BOOM. NEW LEAF.
you can buy it for 6$ on amazon