Superman #136 (1998)

Lois Lane and Clark Kent are sent on assignment to New Mexico, where Superman is expected to assist in the construction of a dam. That evening when Superman completes his appointed task, he meets with Lois. Their meeting is interrupted by X-Plam, a chameleon-like being from the year 2360, where humanity has all mutated into similar beings by a passing comet. He has come to the year 1960 because he had uncovered an ancient newspaper from the Daily Planet with a headline that states Lois Lane is intended to marry a man from the future: namely X-Plam. The vain Lois at first doesn't want to marry X-Plam, however his chameleon-like abilities make him change into a normal looking human, and he retains all his original super-powers.

Superman accepts the fact that X-Plam wants to marry Lois, and finds that he'll be a perfect husband because he's handsome and has super powers. Lois, however still mulls the idea over, thinking about all the other super-beings that have proposed to her in the past. Lois decides to go for it anyway, and the two are married, in spite of Superman's warnings that upon returning to the future, X-Plam will likely change back to his original form. Lois ignores this, marries X-Plam and the two return to the future, where not only does X-Plam turn into his former form, but Lois also is mutated into a similar being.

Realizing that Lois is miserable in the future, he decides to get more fuel for the time machine and bring her back to the present. However, the fuel proves to be highly radioactive, and X-Plam's second exposure to it proves fatal, however he does not die until he successfully gets Lois back to her own time. Back in her own time, the saddened Lois reverts back to her original form, reunited with Superman, they both wish that X-Plam had found the next day's edition of the Daily Planet, the one which reported that Lois had become a widow.