She said she remembered fondly the time during rehearsals when Miss Allen, who didn't know how to pop open a flattened opera hat, learned the technique. In the show, during a scene in which Charity sings ''If My Friends Could See Me Now,'' the actor with whom Charity is having a date gives her the opera hat. Charity doesn't know what it is, or how to open it. The actor shows her, and then she proceeds to use her fingers to open it, then closes it under her arm and giggles. She pops it on her rear, and it opens, then closes it between her knees.