Ditto what everyone said about the simple/odd questions for the first passport (not citizenship application).
I think they also ask some intentionally misleading question to catch out anyone misrepresenting themselves. I was applying based on marriage to my UK husband. The interviewer asked how my visa was connected with my husband's work visa (or something like that). I'm guessing she had all the correct info in front of her, but wanted to be sure I was who I said I was and she seemed pleased that I'd corrected her. It was quite obvious to me, but if someone was lying on the application or sitting in on the interview for someone else, it would have caught them out.
If you are who you say you are, it's easy peasy.