Lamont, after Fred tells Hazel she never looked sweeter, is laughing hard right alongside Fred, but then when they cut back inside the house, he is clearly as forlorn as he had been since Crystal left him at the altar. This clearly shows he broke character to laugh at Fred's joke after he said it.
Lamont, in an attempt to appease Aunt Hazel when she was incensed that she couldn't return a table cloth she bought as a wedding gift because Fred opened it and put it on one of the tables, offered to "buy [her] another table cloth". He probably meant to say he'd pay for the one they used, as she, like the other guests, was planning to return it to get the money back.