In a large heavy pot, heat corn oil over high heat until the oil smokes. Add 1 kernel popping corn and heat until kernel pops. Add vanilla bean and rest of popping corn, cover pot, and shake gently until corn starts to pop. Shake vigorously until popping subsides. Remove from heat. Remove vanilla bean and toss popcorn with sugar, salt, and melted butter.
Scrape seeds from vanilla bean and add to popcorn.
