Here is the full list of all 24 Hidden Kitten achievements.
Find all hidden objects in all levels.
Find all hidden objects in “Eating Habits”.
Find Luna in “Purrmuda Triangle”.
Find all hidden objects in “The Fur-midable Theme Park”.
Find all hidden objects in “A Purr-fect Space Adventure”.
Find all hidden objects in “Enjoying the Ordinary”.
Move clouds around in “Arrival at Milky Bay” ten times.
Start and stop the cart in “Spooky Train” five times in two minutes.
Find Minerva Meowgonagall in “Spooky Train”.
Click all balloons in “Furry Fiesta Funpark”.
Find Fluffoon in “Behind the Ring”.
Lesser cat has gone where no cat has gone before.
Find Lucky in “Ad Astra”.
Destroy all asteroids in “Refueling in Space”.
Move aircraft around in “Chilling in the Park” ten times.
Find Charlie in “A Normal Afternoon”.
Open and close the curtain in “A Normal Afternoon” five times.
Play with the mouse in “Underground Birthday” before touching anything else.
Speed up the Ferris wheel in “The Fastest Bear in Town” to maximum speed.
Destroy all nachos in “Purrmuda Triangle”.
Do the laundry in “Exploring the House” three times.
Knock over pylons in “Meeting the Neighbors” five times.
Watch the stars for five minutes in “Catstrology”.
Move plants around in “Behind the Ring” ten times.