Flavor of the month

Something or someone that is temporarily popular or fashionable but likely to be quickly replaced by the next trend.

This phrase originated from ice cream parlors in the 1930s-40s America, where shops would promote a special 'flavor of the month' to encourage customers to try new varieties. The marketing concept implied temporary special attention before moving on to the next flavor. By the 1960s, it had become a metaphor for any short-lived trend or fad.