She didn't have many funny lines.
One I remember was in the episode when she had a crush on Potsie and sent him unsigned love letters to intrigue him. She met him alone at Arnold's after hours. When he turned her down because she was a kid she sat alone in Arnold's and hid under a table when Richie came in looking for her. Richie picked up her coat and said, "Joanie, I know you're here because I gave you this coat for Christmas". From under the table Joanie says, "I lent it somebody."
That might have been her biggest laugh on the show.
I just nailed Mrs. Trumbull