The central character was Marcia Middlewell, a seemingly average girl who harbored a secret alter-ego. When accidents appeared inevitable or other trouble spots occurred, Marcia would enter a phone booth. With the utterance of her magic phrase, "Zapper jiffy squincher scrum, make me into Thelma Thumb!", she would shrink to the size of a salt shaker and fly to the rescue. Thelma's size allowed the segments to examine objects and places from a unique perspective. Also featured was Marcia's pet magpie, Cyrus, designed by Brian Narelle. As with other Korty shorts, the dialogue was partially improvised by San Francisco-based actors; Judith Kahan supplied the voice of Marcia/Thelma, and James Cranna was Cyrus.