"Sam Beckett Leaps Into Booster Gold" from Justice League #4 (DC, 1987) by Keith Giffen, J.M. DeMatteis, Kevin Maguire and Al Gordon
I'm going to cover every iteration of the Justice League, don't worry, and I'll talk about the 80s League's comedy under Justice League International. Let it be known, however, that the book started out as simply "Justice League", lasting 6 issues and an Annual before adding the extra word to its title. These issues weren't QUITE as comedic, though they were quick to get there once Booster Gold was added to the roster. There was humorous banter, to be sure, but the storylines and subplots had yet to merge into the full-on action sitcom it would eventually become.