Here is the full list of all 23 Purple Chicken Spaceman achievements worth 1,000 gamerscore.
Beat Goosebump Gorge
Beat Outer Space Panic
Killed a boss with a smartbomb
Successfully dodged the wobbly powerdown
Played into the wee hours of the night
Didn't shoot for 30 seconds and didn't get hit
Got rid of the shakes!
Used a smartbomb for the first time
Got your first wobbly powerdown
Used a shield for the first time
All you gotta do is play!
Beat Neptune's Crypt
Beat Frosty Fields
Beat Desert of Desserts
Beat Heck
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
Beat a level without using a powerup
Finish a Level Without Getting Hit