To let the cat out of the bag

Cat: Miaoooowwwwww!
Will: Hello, I'm William.
Graciela: And I'm Graciela. Will, I hope you've brought that poor cat for a very good reason. It's terrified!
Will: Well I wanted to explain an English phrase. And I brought Whiskers to help.
Cat: Miaow.
Graciela: Well he's not very happy about being stuffed into that bag. You'd better hurry up and explain your phrase.
Will: Okay, okay. So, right. I'm going to tell you a very big secret.
Graciela: Oh?
Cat: Miaow?
Will: But you must promise never to let the cat out of the bag!
Graciela: No, we must let him out, he is unhappy, Will.
Cat: Miaow!
Will: No, no. I mean in English, when we say 'you mustn't let the cat out of the bag', it means that something is a secret and that you mustn't tell anyone.
Graciela: Ah, so it doesn't literally mean there is a cat in a bag. It just means that there's a secret that must be kept.
Cat: Miaow.
Will: Exactly. And I brought Whiskers in just to help you remember the expression. If you let the cat out of the bag, it means that you reveal a secret. Listen to some examples.
We need to keep this quiet! If anyone lets the cat out of the bag there'll be trouble!
We were going to have a surprise birthday for dad, but my silly brother let the cat out of the bag the day before.
Graciela: Okay I get it.
Cat: Miaow.
Graciela: But I'm not at all interested in secrets until we get this real cat out of this real bag. I'm going to let it out!
Cat: Miaoooowwwwww!
Graciela: Owwwwww!
Will: I actually meant it when I said don't let the cat out of the bag. Whiskers is a bit crazy.
Graciela: Your cat is berserk, get him off me!
Cat: Miaooowww!
Will: Well, now you'll remember not to let the cat out of the bag next time!