It’s a less Mad world. Starting with issue No. 500, to be published in April, the monthly satirical magazine will become a quarterly, though it will expand to 56 pages from 48. The changes were announced by DC Comics, the Warner Brothers Entertainment unit that publishes Mad. As befits the magazine’s what-me-worry? attitude, Mad’s editor, John Ficarra, said: “The feedback we’ve gotten from readers is that only every third issue of Mad is funny. So we decided to just publish those.” The fate of Mad Kids and Mad Classics is less kind. The final issues of those publications will be Feb. 17 and March 17, respectively.