These galaxies open up after you've found all three Green Stars. For quick reference, they're found in Battlerock, Buoy Base and Dusty Dune galaxies.

Bubble Blast Galaxy
The Electric Labyrinth (first in video)

Rolling Gizmo Galaxy
Gizmos, Gears and Gadgets (2:30)

Loopdeeswoop Galaxy
The Greatest Wave in the Galaxy (3:20)