nine days' wonder

a nine days' wonder AND a nine-day wonder (someone or something that causes interest or excitement for a short period but is then quickly forgotten) — злоба дня, кратковременная сенсация, предмет недолгих толков; ≅ калиф на час (контекст)

a one-day wonder, a seven-day wonder

Example 1: I would be delighted if other Earths harbouring intelligent life were discovered. For most people, however, it would be nothing more than a nine-day wonder (bbc.co.uk).

Example 2: All this shows is that the media have discovered a 9 day wonder over a normal human being who has a fantastic voice. There are a lot of normal people about you know and I guess the current shock and surprise is because the media (gutter press and reality tv) have suddenly had a reality check and had to recognise this fact (from a comment about Susan Boyle on bbc.co.uk).

Example 3:Don't worry about the story about you in the newspaper. It'll be a nine days' wonder and then people will forget. (idioms.thefreedictionary.com).

Also
A one-hit wonder is a music industry term to describe an artist generally known for only one hit single (wiki).

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From A wonder lasts but nine days, and then the puppy's eyes are open