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