A model intrapreneur is Art Fry, a chemical engineer who in 1974 was working in product development at 3M during the week and singing in his church choir on Sundays. He was accustomed to marking the pages in his hymnal with scraps of paper, so that he could quickly locate the songs during the two services at which he sang. The procedure worked fine for the first service, but often by the second one some of the loose scraps of paper had fallen out of their places. Fry, not having noticed this, was sometimes at a loss for words. —The Evolution of Useful Things,
Henry Petroski

What made Fry start thinking about an invention?

singing in his church choir
the failure of bookmarks
an article in the Sunday paper
the success he had locating songs