The Awful Truth scene

My favorite scene in the movie. It's towards the end. Lucy and Jerry Warriner's (Irene Dunne and Cary Grant) divorce is almost settled. It will be completed at 12midnight tonight. Jerry is engaged to an heiress and is just waiting for the divorce to be finished. He arrives at his fiance's house to enjoy some cocktails with her family. Lucy Warriner pretends to be his sister and crashes the party. Making a mess out of everything.
This movie is said to have been mostly adlibbed and both Irene Dunne and Cary Grant are masters at it. Irene Dunne is hysterical and if what they say is true than these words are mainly her own and were not written for her. When she dances to the song "Gone With the Wind" it has been confirmed that her "i never could do that" is an adlib.