When we started helping out a single mom in our neighborhood a couple of years ago, I bought an old stroller for two kids. It must have been at least 15 years old, ugly and heavy, both strongly built. I then had in mind a future soap box car since the modern strollers are not exactly built for that but then it all just came to nothing. But since the stroller has been standing there for quite some time now, the kids turning five this year, we just decided to make it happen. You could call me the product owner. I just said to my husband that wouldn't it be nice to build that soap box car now? I imagined the simplest possible thing, built in a couple of hours, but now, four days later, we have this monster (which we have no idea where to put) which takes at least three kids and with a braking functionality.
So, what is the conclusion on this? Well, as always as a product owner, you will have another mental image of your requirement and how hard something should be. But it's also interesting how we all felt that this became so much interesting that my original idea of a soap box car. (B t w, all I did was pain the thing)