"Nine day wonders" is a phrase used to describe something that is temporarily popular or admired, but quickly fades from public attention. There are many synonyms that can be used to describe this phenomenon, including flash in the pan, passing fad, and transient trend. Other similar phrases include here today, gone tomorrow, short-lived sensation, and momentary craze. All of these expressions capture the same idea - that something has captured public attention briefly, but is unlikely to endure for long. While it's always exciting to see new things capture our interest, it's important to recognize the difference between passing infatuations and enduring innovations.