Not all questions you are asked in an interview will be logical ones that are directly related to the job itself.
Remember, we all have a different personality and some hiring managers you speak with might be a bit unconventional.
Some questions are asked just to gauge your reaction to them!
Some individual hiring managers and some companies might ask legal interview questions that could be described as trick questions or stress questions that are used to test your ability to think on your feet and to test your reasoning skills.
Here are a few such questions that I've heard asked during some interviews:
Describe yourself in 5 words. Yikes. How can you summarize yourself in five words? Think of five words that properly describe you, highlight your character and that would be of benefit to the company and to the job such as: organized, intuitive, ethical, trustworthy, honest, professional, fair, enterprising, entrepreneurial, focused, etc.
Take your pick.
What hobbies do you have? Don't include your hobbies and personal interests in your resume. In an interview setting, this is when mentioning your hobbies might have some merit. If you are an avid guitar player and see that the interviewer has a picture of themselves playing a guitar, this might be a good opportunity to casually mention your common interest in the guitar. People hire people that they like and if you can establish a commonality with the interviewer, it can only help you.
What is your greatest achievement outside of work? If you have a family, perhaps your greatest achievement is raising your kids. Perhaps it's the time you donate to a special charity. It might be getting your university degree. Think of an achievement that highlights your personality and indicates a balanced life outside work.
What magazines do you read? Maybe you don't read much at all! In this case, focus on things that you do read: newspapers, books, e-books, etc. If you do any reading that is work-related, mention it.
What tv shows do you watch? Do you watch shows that are business-related or that apply to your industry or work? If not, try to think of a show or two that won't make it look like you spend all your free time on the couch.
Do you think I'm a good interviewer? If it will help you get the job, yes! I have actually heard this question asked before. Perhaps the interviewer was looking for positive reinforcement. Give it to them, just don't kiss their butt.
Tell me about your family. This might be considered a borderline legal interview question depending on where you live. I've been asked this question before and it just seemed to me that interviewer was generally interested to learn more about my family, nothing more. They might be family-oriented themselves especially if they work for a family-run company.
Sell me this pencil. I actually had this question asked of me during an interview. I was interviewing for a sales position and I had to "sell" the pencil to the interviewer. FYI, my answer to this question was to offer the pencil to them for free to try for one week with the intention of returning after one week to see if they liked the pencil enough to buy it...
There are three people on a desert island and there is one boat, one bag of nails and a roll of tape..... In other words, they give you a situational question that appears to have nothing to do with the job you are interviewing for but appears to be testing your perception and reasoning abilities.
Not all interview questions you are asked will be directly related to the job. Not all interviewers are skilled either so you never know what questions you will be asked.
The best thing you can do is try your best to properly prepare for questions you might be asked and to not allow yourself to be caught off guard.