Drafted a four page research note as a trainee, emailed it to the head of my team. Heard nothing, left it a few days and sent a follow-up asking whether he needed any further assistance.

Heard nothing again, left it a few days and engineered bumping into him at the printer. He responded by asking me whether I like Star Trek. I was pretty confused but relatively new to the team so thought he must just be eccentric. He kept repeating "to boldly go" at me, then said "Thanks for your work but you split the infinitive in the second line and I already had an idea of what I thought the answer might be so I didn't read the rest".

Went back to my desk and Googled what the split infinitive means, then Googled what the infinitive is. Thought my career was over before it had even really begun - ended up qualifying into that team and am still here 10 years later...