SPOILERS FOR CAT ON A HOT TIN ROOF, CAROLINE OR CHANGE, AND AUGUST: OSAGE COUNTY
When I saw Cat, I also thought the audience's raucous laughter was bizarre. I did not feel it was directed in a way to bring out so much laughter during serious portions -- it really was unclear why people were laughing so much. I spoke to two of the cast members about it at the stage door, one of whom felt that it was cultural, but the other one also seemed baffled by the response.
I think it is tricky when a production sets up certain lines as laugh lines, and then follows up with lines that are supposed to be taken at face value. During August: Osage County's infamous dinner scene, a lot of the laughter is of the "she did not just say that!" variety, but serious lines are mixed in. I've seen the show 3 times -- the first time, when Violet says that her sister has dents in her skull from protecting her from the claw hammer, there was an appropriate hush in the room. The second time, everyone seemed to think it was hilarious. The third time, one person laughed, but very briefly as if the person was thinking, "Wait, that's not funny." I didn't notice any particular change in performances that would have led to such varying audience responses. I'm interested in hearing what other people noticed in audience response when they went.
I saw Caroline or Change twice (not on Broadway) -- people laughed each time at the "Jews go to Hell" line but also briefly in the "Wait, that's not funny" way.
"What was the name of that cheese that I like?"
"you can't run away forever...but there's nothing wrong with getting a good head start"
"well I hope and I pray, that maybe someday, you'll walk in the room with my heart"