This is the most god-awful stock photo of a job interview we could find
You've probably heard of some bizarre interview questions being asked candidates or maybe even asked a few yourself. This makes more sense than one might think.
The first job I ever had was one where I actually managed to get hired without being interviewed at all. A friend of mine "sold" me to his boss as a hotel porter so well that she agreed to take me for the summer without ever seeing me or talking to me. That worked out nicely but hiring people you know nothing about generally is like getting married without meeting the person first. Wouldn't recommend it.
There's a bunch techniques that HR people and managers have developed to vet people during interviews, but speaking plainly as a person that has no formal HR training, just a bunch of hiring experience – you have to ask candidates weird questions. Why? Because reactions to unexpected questions are the only ones that count as truly authentic.
Let's say you’re hiring a project manager for your software development company. The classical interview might have some questions like "What do you consider your strenghts and weaknesses?" or "Where do you see yourself in 10 years?". Those questions are fine to ask, but they don't exactly surprise the applicant. If you show up to a battle in a tank, that will be expected - bring a big hot-dog shaped blimp too and confuse the oponent!
Ask crazy random questions and see what happens. "What do you think of the intergalactic conspiracy of the crab-people?", "Do you think bears are good people? Explain your position!", "When was the last time you smoked weed?". The last one might be a serious HR violation in certain parts of the world, so tread carefully, but the point remains the same – ripping a candidate out of her comfort zone brings out sides of them that usually stay hidden.
Doing the usual "Why should we hire you?"/"I am very passionate and my experience would contribute to your company“ blaah-blaah is not bad but to hire extraordinary people you need to see how they act in extraordinary circumstance.
It goes without saying that there are situations where this might not be a good idea at all. But generally there are few positions that require no human interaction at all. And you will want to know how they deal with unexpected situations.