Superman… On a Marvel comic? It can only be the hype machine (and some timely opportunism) surrounding SUPERMAN THE MOVIE again.
This is the first edition of MARVEL UK's FRANTIC, a test-the-market one-shot published in the Summer of 1979.
This was one of the first wave of seasonal specials launched under the Marvel Revolution. Up until this point, the New York masterminded operation had believed imported magazines and Treasury Editions more than sated British demand for extra Marvel goodies.
Dez, on the other hand, already had a career in British comics and understood the local market far better. He also had a brief from Stan to grow the UK operation and not only did specials allow him to do that but they were also handy test-the-water tasters to see whether readers and retailers would be receptive to a new launch without all the risks of a costly failure.
I've already posted the FRANTIC WINTER SPECIAL from the end of 1979 and, buoyed by the success of the pilots, this MADalike (which swiped much of its content from CRAZY, Marvel New York's Mad knock-off) returned as a regular book the following year.
Of course, Dez had been a former editor of the UK edition of MAD so he knew all about repackaging US humour to try and make it more attractive to British sensibilities.