Here's an interesting piece of information!

What is a cat-related

idiom that you can use when a secret is revealed or when previously hidden information comes out in the open?

You can say, "The cat is out of the bag"!

Put it in an example, you'll get, "I was planning to surprise my friend with a birthday party but the cat's out of the bag now because she saw the gifts in the room".

I must say my cat, Griffin, doesn't look too happy about it! 🐱