Go to Shiver burn galaxy. Then at the start of the level press the up arrow to go to camera mode. Look backwards and all the way up. On top of the dark blueish purple wall there should be 3 mysterious figures.*
Ok, When you and a friend are playing in Co-Star mode, The person playing as the orange Luma(Player Two) Can press the Plus(+) Button for an in-game Applause. The person can also press the Minus(-) Button for a "Booo" Sound to play in-game.
guys I found a a hint and here's what you do: go to throwback galaxy and go to mission silver stars and get the clowd flower and do a long jump then form a cloud, then again, then again and look what you found but the start :