“I’ve got an Ace up my Sleeve” is a phrase commonly used to tell someone that you have a secret plan that you’ll keep a Secret until the time to reveal it arrives.
If you are Suzie - the Scottish Fold Cat’s Mom, however, you could get away with saying “I’ve got a Cat up my Sleeve”.
Watch Suzie the Scottish-fold Cat, hanging out inside the sleeve of her Mom’s Jacket
Hilarious right? I am still on the floor laughing! ROFL!!