Pop popcorn - about two normal size bags (microwave)
Put in small saucepan the butter, Karo, and sugar. Cook on medium-high heat until all melted and just boiling.
Place popcorn in large plastic bowl. Pour caramel mixture over the top. Stir till evenly coated.
Put two large pieces of wax paper together, just overlapping, on the table. Dump out popcorn mixture and spread out a bit.
As soon as it is a little cool...eat it!