Push the two twin beds together. Push the bed frames as close together as you can.
Push the mattresses together as tightly as they will go.
Place a king-sized foam mattress topper or memory foam mattress topper on the bed.
Place a feather bed with a fitted bottom over the two mattresses and mattress topper. The fitted bottom will help the two mattresses from sliding apart while also making the gap between the mattresses less noticable.
Place king-sized sheets and a king-sized comforter on the bed.