In addition to the original story with updated graphics and gameplay improvements, Bowser Jr.'s Journey is a brand new side story that follows "Bowser Jr. as he gathers an army, creates formations, supports his allies with an arsenal of moves and generally causes chaos (in the best way possible)." In our review of the original Mario & Luigi: Bowser's Inside Story, we said that this entry was "easily best in the series thanks to its focus on a completely outlandish script and the epic battles."
In the latest Nintendo Direct, 3DS still had a few games shown besides Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, including Kirby's Extra Epic Yarn, Luigi's Mansion, and Yo-Kai Watch Blasters. Adam Bankhurst is a news writer for IGN and is excited to dust off the old 3DS to try this next year because he's heard great things. You can follow him on Twitter @AdamBankhurst.