Does anyone know cute short phrases or words to make someone sound witty?

In my experience, anything that is used insincerely, out of your own time period or sounds rehearsed has the opposite effect. You sound younger and less clever than intended. That said, myself and others I know have a long running joke using the words groovy, moxie and gumption. We use them rarely, mostly with each other or for comedic effect. Use it too much, and it’ll turn on you.