Here is the full list of all 23 Purple Chicken Spaceman achievements worth 1,000 gamerscore.
Beat Outer Space Panic
Beat Goosebump Gorge
Beat Neptune's Crypt
Beat Frosty Fields
Beat Desert of Desserts
Beat Ocean Scenes
Beat Alien Holmworld
Beat Attack on Earth!
Beat L4Z0r C4t for a second time
Beat the game
Finish the game a second time
Use a smartbomb for the first time
Get your first wobbly powerdown
Don't let the wobbly powerdown touch you!
Use a shield for the first time
Get your kids in bed and stay up way too late playing games
All you gotta do is play!
Get rid of the shakes!
Beat a level without using a powerup
Deliver the finishing blow to a boss with a smartbomb
Don't shoot for 30 seconds without getting hit
Finish a Level Without Getting Hit