My old Betty Crocker book says:
Popcorn Balls
1/2 C. sugar
1/4 C. margarine or butter
1/2 cup light corn syrup (Karo)
1/2 teaspon salt
Few drops food color (if desired)
8 Cups of popped popcorn
Heat all ingred.s except popcorn to simmering, in a Dutch oven over med-high heat, stirring constantly. Stir in popcorn and cook stirring constanty until popcorn is well covered, about 3 minutes. Cool slightly and roll into balls with wet hands. Set on waxed paper. Cool completely and wrap in plastic wrap or place each in a plastic bag.
For Caramel Popcorn Balls:
Substitute packed brown sugar for the white sugar, and use dark Karo instead of light. No food color.