It's possible you're thinking of:
* "Cat's meow": This idiom means something that is excellent, very good, or the best.
* "Cat in the cradle": This is a song and its title refers to the idea of a father who is too busy for his son, only to find out later that his son is now too busy for him.
If you could provide more context about where you heard this phrase, it might be possible to determine the correct idiom you're looking for.