Here is the full list of all 15 Find the Orange Narwhal achievements.
Finish the game once
Help the Pirates
Help the Ninjas
Help the Police
Help the Mermaids
Help the Clowns
Save the King from the Zombie Apocalypse
Finish a playthrough without needing to respawn
Join the Horde today!
Go out with a BANG!
Fail to resist arrest
Get distracted by the Sirens' call
Fly the flag at half mast
Leave your temples at the temple
Get thrown in the slammer