Perhaps not "best", but certainly most amusing, so what the heck!

Years ago as an intern, I applied to a large pharmaceutical company. On part of the application form, you had to enter the code of the department you were applying to.

What I *should have* put down was "IT", which is the department that houses all their devs. However, I didn't actually read any of what the codes meant, assumed that was the department for helping people with how to mail merge, and put down "COMPSCI" instead. This was computational sciences - loosely summarised as computational data analysis on various druggable molecules.

I do *not* have any sort of biology or chemistry background, so the interview was rather... interesting, and I muddled through on the basis of getting some more interview practice assuming it was a no go.

To my amazement, got a phone call saying that they'd been thinking they wanted someone more technical on the team, and despite my lack of scientific experience they thought I'd be a good fit. I was unsure as to whether I should accept for a while, but then decided to just go for it - and had a fantastic internship there, working on a great variety of stuff, and learning tons all under a supervisor who I'm still in touch with to this day.

tl;dr - Applied for the wrong job. Coincidentally got it anyway, and miraculously had a fantastic year working there.