A nine days’ wonder
Definition 1 of 1
Pro Tip 1/3Brief Popularity
Use this phrase when something is trending or popular for a very short time, then fades away. 
The meme was a nine days’ wonder, spreading like wildfire and then disappearing.
Pro Tip 2/3Fleeting Interest
It implies that the public's interest is temporary and not deep, often following a fad. 
The diet fad turned out to be just a nine days’ wonder.
Pro Tip 3/3Not Enduring
It suggests that the subject will not have lasting value or impact. 
Everyone thought the show would be a hit, but it was just a nine days’ wonder.