She only wanted $17.50
Ellen Corby (June 3, 1911 – April 14, 1999).
Ellen Hansen Corby was an American actress and screenwriter. She is best remembered for the role of Esther "Grandma" Walton on the CBS television series The Waltons, for which she won three Emmy Awards. She was also nominated for an Academy Award and won a Golden Globe Award for her performance as Aunt Trina in I Remember Mama (1948).
During the bank run in It's a Wonderful Life, Ellen was one of the customers asking for her money. In the script and in the rehearsals, Ellen was to ask for $17, which she did. Before shooting the scene, though, director Frank Capra took Ellen aside and told her to ask for $17.50. He said it would be funnier, so she did. Both Jimmy Stewart's and Ellen's reactions were genuine, unexpected, and delightful.
Corby guests in "The Gift Shop" on The Donna Reed Show (Season 7, Episode 23).