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