In September, the restaurant chain Denny’s tweeted “hashbrowns on fleek,” seizing on a slang phrase that was permeating the Internet to promote its breakfast side dish.

The message, which to teens translates to “these hashbrowns are on point (very good),” garnered almost 30,000 retweets and was seen in the advertising industry as something of a social media marketing masterstroke. Taco Bell and IHOP later sent out their own tweets using the phrase “on fleek,” looking to get in on the action.

...