Here is the full list of all 21 Woah Dave! achievements.
Your name is POO!
Destroy a Woah Block with another Woah Block!
Let a Woah Block get blasted by a UFO!
Get killed by a UFO beam!
Collect two hundred pennies!
Let two platforms get blasted by UFOs!
Kill a UFO!
Collect one hundred pennies!
Throw a Woah Block in the Lava!
Hit an Eyebat!
Kill 10 or more enemies with 1 Woah Block!
Earn your first penny!
Collect three hundred pennies!
Collect four hundred pennies!
Collect five hundred pennies!
Collect one thousand pennies!
Defeat the mothership in Peoria!
Defeat the mothership in Fort Bragg!
Defeat the mothership in West Haven!
Kill a rare alien!
Ride a UFO!