- "Even heroes need a hand sometimes! If you have one more Wii remote, a friend can help you. Your friend can stop enemies with the A button and then shake the Wii remote to spin them into the air!"
- ― Co-Star Luma on Starship Mario explaining to Mario/Luigi about how co-op mode works.
While the Co-Star Luma cannot stun any bosses, it can still stun medium sized enemies such as Chomps (for example in the Chompworks Galaxy) so you can grab the Comet Medal easier or the Boulder Bowl Galaxy to force Boulders and Chomps to collide so you can guide the Goomba to the Gearmo.
The Co-Star Luma can do what the Player 2 could do back in Super Mario Galaxy except even more. It can stop and squish small enemies (such as Goombas, Koopa Troopas, and more enemies) and objects like rolling rocks. A new feature lets Player 2 make the Luma pass objects to Mario, such as 1-Up Mushrooms, coins, and power-ups but it can no longer make Mario jump.