How to get cats pajamas?

Excuse me, could you please elaborate on the phrase "get cats pajamas"? It seems like an unusual expression that's not immediately clear to me. Are you referring to a specific type of clothing for cats, or is it a colloquialism I'm not familiar with? Could you provide some context or explain what you mean by "cats pajamas" and how one might go about acquiring them? It would be greatly appreciated if you could clarify this for me.