Here is the full list of all 25 The Mystery of Caketropolis achievements.
Delivered Cerio's invitation to Ol' Smokey.
Witnessed the Caketropolis Fire.
Met Verdori in his lair.
Witnessed the scene of Maggis's murder.
Found evidence in the warehouse.
Found evidence in Cerio's house.
Solved the mystery of Caketropolis. Or did you...?
Opened the safe in Rimentus's den.
Restored harmony in Stalagshire.
Returned the missing pages of Yri's journal.
Cheered up Faul.
Attended Insignium's speech.
"Reunited" Insignium and Fleur
Received a gift from Artist Jern.
Completed the Enforcers' treasure hunt.
Stole a slice of Cerio's cake.
Beat Verdori without taking damage.
Cheered up Despondent Haley.
Convinced Negative Nathan to attend Insignium's speech.
Convinced Baker Will to attend Insignium's speech.
Didn't let society dictate how you should behave.
Disabled Insignium's doorbell.
(Nearly) suffocated while escaping.
Gave Fleur what she asked for... Sorta.
Ignored a threat and paid the price.