He thought he was pretty good at his job and took a second job. His coworkers (included me) felt like he was slimy and was not good at his job.

Everyone was suspicious of the dude and finally one day his boss’s boss called him for an emergency, and he said the company name while answering his phone… the other company he worked for.

Company fired him, told the other company, and threatened to sue him. He paid back a good chunk of his recent salary (they didn’t need the money I suspect wanted to make an example).