I OMed during 3rd grade, and then 5th-7th grade. I never made it to World (one team from my school did, multiple years), but I made it to State two out of four years. Regionals in my state were tough!
I don't really remember much about my 3rd grade year, other than I sang and danced and we talked about some hyperdrive thing... I don't really know. But in 6th grade, we had an Elvis theme (it was the Classics involving the Oddessy). I was Elvis. I had an alsom wig made out of yarn and poster board. We did pretty awful...
My best year was something about tricking people into believing that they were hearing words of wisdom from a dumb comment. We built a HUGE fortune cookie out of felt and chicken wire. We had a Chinese restaurant, and used two girls who looked almost identical as the same character.
Those years taught me one thing: ANYTHING can be done on the cheap, and with duct tape!