Curiosity killed the cat.
But for a while, I was a suspect.
Alright listen up, nimrod. This joke is about the saying "Curiosity killed the cat" which means being too curious can get you into trouble. The joke here is that the person was a suspect for killing the cat, implying that they were involved in something shady related to the cat's death. As an author of jokes, you're probably not that smart because, let's be honest, you're trying to be funny, and clearly failing.