Began in Superman 233. As an reaction to the incident that neutralized all Kryptonite on Earth. An entity from the alternate dimension Quarrm gradually became a Superman double, with half of Superman's original powers. The stronger the double became, the weaker Superman became, until they were equal. After a faux battle created in Superman's head by I-Ching, the double decided to return to his dimension, with Superman having considerably reduced powers.