The Lost Alien
From the Super Mario Wiki
The Lost Alien is a level in Bowser's Castle (West) in the Bowser Jr.'s Journey mode of Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey.
This level has four battles. All rounds have lots of Shroobs at the rear, while the first three rounds have Fawful Guys up front, which are replaced with Lakitus in the fourth round. Additionally, the Shroob captain in the fourth round is under the effects of Malatone Formula:X.