Here is the full list of all 39 Planet of Mubu achievements.
Find O!
Find the blue cube!
Destroy the world!
Complete The Run Zone!
Find N!
Complete The Forest Zone!
Complete The Boss Zone!
Complete The Puzzle Zone!
Find L!
Complete The Arena Zone!
Complete The Viking Zone!
Find Q!
Find Z!
Complete The Maze Zone!
Find Y!
Find W!
Find X!
Find the red cube!
Find V!
Find U!
Find T!
Find R!
Find S!
Find P!
Find M!
Find H!
Find I!
Find G!
Find F!
Find D!
Find the green cube!
Find E!
Find A!
Find C!
Find B!
Find K!
Find J!
Complete The Tutorial Zone!
Start the game!