While they were gone to music class, I lined up a bunch of same height desks, made a butcher paper belt around it and readied the fruit in bowls. When they came back I welcomed them to their first day on the job at the fruit salad factory. I explained how the assembly line worked and what the jobs were.
Everyone was assigned a job and we set to work. Someone pulled the paper slowly to move the line down (girl kneeling at the end of the line), someone placed the bowls onto the line, others added one spoon each of their particular fruit as the bowls moved down. One child at the end was in charge of shipping and receiving and he unloaded them from the belt and gathered them on a few empty desks. In about three minutes it was all over and we could enjoy our fruit salad and discuss the process. We talked about what different specializations we had, what natural resources we used- both renewable like the fruit and non renewable like the plastic spoons. We discussed the capital resources, like the assembly line machine and the building as well as human resources- us.
I was shown this project by another teacher my first year and have done it several times since. At my old school, we were able to do it in the cafeteria and line up several really long tables. We have 3 third grade classes work at once and it was a big production This was a scaled back version for sure, but just as fun and memorable.