There have been so many interview fads it's hard to remember them all, but a particularly disagreeable fad was the "surprise question." You're being questioned

There have been so many interview fads it's hard to remember them all, but a particularly disagreeable fad was the "surprise question." You're being questioned about some programming-related thing, and then in the middle of it they want to know how many monkeys you can stuff in a milk crate, or how to develop an optimal strategy for playing roulette. I suspect a lot of interviewing fads are because interviewing is a long and boring process, so changing things up brightens their workday. But I never had any reason to believe any of them had any connection with discovering the optimal candidate.