Here is the full list of all 21 Woah Dave! achievements.
Defeat the mothership in Peoria!
Collect two hundred pennies!
Ride a UFO!
Get killed by a UFO beam!
Let a Woah Block get blasted by a UFO!
Destroy a Woah Block with another Woah Block!
Your name is POO!
Let two platforms get blasted by UFOs!
Throw a Woah Block in the Lava!
Kill a UFO!
Collect one hundred pennies!
Kill a rare alien!
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 Fort Bragg!
Defeat the mothership in West Haven!