Margaret had a cameo role as the seasick elderly woman, Miss Gaulswallow. It was producer Jerry Epstein who recommended Rutherford for the role but Charlie was hesitant and accused Epstein of only wanting "stars." But Epstein thought Rutherford would be perfect. Charlie finally gave in and agreed to meet with her:
Charlie, at his most charming, greeted her with open arms. "How nice of you to come. Would you consider playing such a small part for me? It would be such a privilege to have you." Rutherford was completely bowled over: 'It would be a privilege for me to work with you," she said.
....
It was now time to shoot Margaret Rutherford's scene. Charlie was embarrassed that her part as a seasick passenger was so small, so he improvised more business. He placed a multitude of colored ribbons on her bed, and every time she looked at the yellow or green ribbons, she'd feel faint and want to retch. She was so funny, she had the whole crew laughing. Poor thing, she was ill at the time, and was delighted that the scene required her to be in bed.
Oona was always present when we ran Margaret Rutherford's rushes. No matter how often she saw them, she always laughed hysterically. The scene brought the house down in the movie theaters too. And Charlie was most pleased.(Photo and excerpt from Remembering Charlie by Jerry Epstein)
You can watch Margaret's scene here:
http://youtu.be/SiD_12kkn4s?t=13m51s
...and here:
https://www.youtube.com/watch?v=Xhjn50CxzEs
You can also watch the entire film on youtube. It's not Charlie's best by any stretch but it's worth viewing, if anything, for the music (composed by Charlie), Patrick Cargill (who is great as Hudson), and to see Charlie's brief cameo as a seasick steward.
Extra note: At the beginning of Miss Gaulswallow's scene, she tells the nurse to take the flowers out of the room because they "take up all the oxygen." Evidently Charlie himself felt the same way about flowers, according to his son, Charlie, Jr. Although he loved them, Charlie never wanted them in his bedroom because he felt they absorbed oxygen.