I would strongly recommend "The More the Merrier" with Jean Arthur and Joel McCrae (one of the funniest movies of the period). You may also want to check out "Only Angels Have Wings," although it's not necessarily a comedy (though it does have funny moments). Since you like Hepburn and Tracy, you may enjoy "Without Love". It co-stars Lucille Ball (who practically steals the movie she's so funny). "Stage Door" is another one with Hepburn, though it is a little more popular and you may have seen it. Ginger Rogers and Lucille Ball both co-star and they are truly fantastic. Rapid, witty dialogue. Finally, and a little more recent (mid-70's), is "Robin and Marian" starring Sean Connery and Audrey Hepburn. Truly funny to watch a tired, aging Robin Hood look up Maid Marian (who's become a nun) only to hear Marian say, "What the hell do you want?"