I like MUTT AND JEFF, one of the earliest successful US comic strips and one that ran for nearly a century…if it's not STILL running somewhere. But I've never understood why it was so successful in comic books.
Many newspaper comic strips were reprinted in comic book form. In fact, that's how comic books got their start. Through the years, everyone from LITTLE ORPHAN ANNIE and SMILIN' JACK to KERRY DRAKE and BIG CHIEF WAHOO had their own comic reprinting newspaper strips.
But MUTT AND JEFF just seemed to keep on going. Appearing in some early collections, the iconic short/tall duo were initially cover-featured in FAMOUS FUNNIES, had reprints used as filler in ALL-AMERICAN COMICS and got their own title from DC in the early forties. No matter what the climate in the industry, DC promoted M&J as one of their biggest selling titles! After 19 years, Dell took over the title and later--as seen in the above ad--gave it up to Harvey. It must have been a success for Harvey because they actually had spin-offs!
By the time the comic book ended in the mid-sixties, there were literally NO comics left reprinting newspaper strips! MUTT AND JEFF were there at the beginning and there at the end!