Fads

A fad is any form of behavior that develops among a large population and is collectively followed with enthusiasm for some period, generally as a result of the behavior's being perceived as novel in some way. A fad is said to "catch on" when the number of people adopting it begins to increase rapidly. The behavior will normally fade quickly once the perception of novelty is gone.
The specific nature of the behavior associated with a fad can be of any type including language usage, apparel, financial investment, and even food. Apart from general novelty, fads may be driven by mass media programming, emotional excitement, peer pressure, or the desire of 'being hip'.
Though the term trend may be used interchangeably with fad, a fad is generally considered a fleeting behavior whereas a trend is considered to be a behavior that evolves into a relatively permanent change.