Here is the full list of all 41 Castle on the Coast achievements.
Activate the hidden player 2 camera mode
Drive a submarine into the library?
DETONATE your save file.
Cheerfully wave 30 times
Take down 15 suites of armor
Reach the peak of one of the large, distant mountains on the mainland
Reach the top of the distant, ocean tower
Escape the confines of the playable castle area
Turn on co-op mode
Unlock all costumes
Unlock the secret costume
Discover the secret ocean
Play the world's largest musical instrument
Reach the highest point of the castle. Wow!
Defeat 20 of your bretheren in wood
Drive a car into the library
Beat the game!
Collect every star
Collect every moon star
Collect every spiky star
Obtain the stunt park's keystone
Unlock Vendrick's costume
Unlock Aleandra's costume
Defeate Vendrick and obtain the rainy cathedral keystone
Unlock the mecha costume
Accumulate 1,000 unspent petals
Collect every orb star
Spin a character 10 times
Spin a character 30 times
Bounce off a character 30 times
Bounce off a character 10 times
Defeate Aleandra and obtain the forest keystone
Find a hidden ball
Customize your appearance while wearing the kid costume
Unlock the jetpack
Unlock your first costume
Arrive at the Castle on the Coast
Make friends with a shark, awwwww...
Survive an alternate dimension
Obtain the ocean's keystone
Taste defeat for the first time.