BabyPlanking was... an inebriated creation. I was working for an agency in Chicago at the time, and my coworkers and I had a few drinks at a work party. Planking was sweeping the nation at the time, and one of the colleagues had a baby, and said "I should take some pictures of [my baby] planking." The rest happened very quickly, this workplace being a web development agency. I designed the layout, and the site was up before the weekend was over. I modified an existing image upload plugin to handle user image upload functions, and it gained quite a bit of momentum that year.
Unfortunately, the planking fad was over as quickly as it started, and the site became pretty silent - it is offline now.