What are undercover coders you personally met?

An undercover coder is a non-IT professional who secretly writes code to gain advantage over his less skilled colleagues.

I knew an accountant working in enterprise consolidation business. Not a layman accountant but a regional CFO at a major multinational company. He coded websites in PHP in his spare time and wrote thousands of lines of of Visual Basic at work to process dozens of Excel documents. None of his colleagues knew he could code, so they were amazed at him sipping coffee while they were working around the clock to meet deadlines. He moved on to become a CFO at another multinational later on.

Another time, I met a sales guy working for a conference organizer. He broke his leg once and, working from home, he designed a conference management system around the company website. Not even his boss understood what he did. For years, everyone in the office took it for granted that they had ticketing, scheduling and other bells and whistles available to all conferences through their own website. He had to come out when giving resignation and they barely had time to hire an IT team to replace him.