a one-day wonder

A person or thing that generates interest for only a short amount of time. The band's biggest fear was becoming a one-day wonder, soon to be forgotten when the next big sound hit the airwaves.

A one-day wonder or a nine-day wonder is someone or something that is interesting, effective or successful for only a very short time. If the goal was simply to make people aware of environmental problems it was a great success. Our fear, though, is that this may prove to be a one-day wonder. When such an incident was occasionally reported in the press it was a nine-day wonder. Note: Other numbers can be used instead of one or nine. The right-wing politician had until recently been dismissed as a seven-day wonder following the success of his party in local elections. Note: `A nine-day wonder' may be related to the Catholic `Novena' festivals, which last for nine days.