Firstly, I had chipotle for lunch. When I got home from school my mom was telling me that her minivan was making a noise under acceleration. I took it for a short (no license yet, couldn't go too far on my own) drive and then took a look under the hood. I researched a bit and concluded that it was just a loose heat shield.
Naturally my dad pretty much completely doubted me so when he took it to his mechanic and the tech agreed with me I was feeling pretty happy.