Him: I can't figure out why (some random bug) is happening. It's really weird, and it doesn't make any sense.
Me: It's because of X. You need to do Y and then it will work.
Him: Oh! You're right! That's exactly what it is.
Bear in mind that I have never looked at a single line of this code. I just knew exactly what the problem was, and I knew right away... it wasn't like I had to puzzle over it for a while.
What's your superpower?