Left and Right Wings
From the Super Mario Wiki
The Left Wing and the Right Wing are two items found exclusively in Mario & Luigi: Dream Team. Mario and Luigi are required to retrieve them to restore the wind generator near the north entrance to Mushrise Park.
The Right Wing is found over to the remote east, atop a boulder. Mario must simply hammer the boulder to retrieve it.
Once both are retrieved, Mario and Luigi must give them to a Brock near the generator, who will proceed to restore it, allowing the Bros. to resume their chase on Brickle.