George Dantzig arrived late to class, found some problems on the board and copied them down assuming they were homework. He took them home, worked them out. A couple of days later he gave his work to his professor, while apologizing for taking so long, because the questions were a bit harder than usual.
What he didn’t know was that those questions on the board weren’t homework, but some examples of unsolved problems that were being discussed in class.
A year later he asked his professor for help choosing his thesis topic and the professor just told him to put those two problems in a binder and he’ll accept them as his thesis.