Fun video-Dave Plummer (formerly MS) made zipfolders pre-hiring which MS decided to buy post
Fun video about this - Dave Plummer (formerly Microsoft) made zipfolders before he got a job at Microsoft, and MS decided to call up the creator to license it without realizing he was an employee. It was a sticky situation, and in fact a competitor tried to get him fired, etc., etc.. Cool, insightful story IMHO.
Personal story, a friend of mine got a job offer and in his contract was a page stating all his existing IP/patents had to be offered to his new company on very favorable terms and he would not be able to license sell them. He questioned that page in his contract, and they instantly swapped it out for a better one that they *already had*. So if you see terms in your contract you don't like, ask about them - don't ask, don't get and your new corp. overlords will ask for all they can get in a heartbeat.
Lesson for everyone - get something in writing covering your existing IP/side hustle before getting into the job.