"The in thing" is a phrase used to describe something that is currently popular or fashionable. There are many synonyms that can be used to express this concept, such as "the latest trend," "the hot item," "the cool thing," or "the current craze." Other possible synonyms include "the must-have," "the hip thing," "the popular choice," or "the flavor of the month." Some more creative and informal synonyms might include "the bomb diggity," "the bee's knees," or "the cat's meow." Regardless of the synonym used, the idea is to convey an object, idea, or activity that is currently the talk of the town.