My team and I were ghost developers to many companies, developers, and book authors in the hay days of Macromedia/Adobe Flash.

We were approached to build a bunch of learning lessons for teachers to teach kids - primarily focusing on human anatomy. Instead of building separate lessons, we built a generator tool for the teachers to drag and drop various combinations and permutations that produce almost infinite lesson variations.

The end customer was Pearson Publishing, and I heard they won awards and stuff. Our client was a good person and even paid us extra for doing the better version of the product they had in mind.

That tool was like this and a few others, as mentioned in the comments. But all in ActionScript Flash, complete with sounds, laughter tracks, and ever-expanding sprites of body parts. It was one fun and fulfiling product.