Rodentia Ratburn (also known as Ms. Ratburn) is Nigel Ratburn's sister. She appeared in "Arthur's Substitute Teacher Trouble" as a substitute teacher for her brother when he was losing his voice. At first, Arthur and his friends were afraid her teaching skills might be more difficult than Mr. Ratburn's, due to the fact that Mr. Ratburn is the strictest teacher at Lakewood Elementary School. However, after Ms. Ratburn arrived into the classroom, her teaching skills turned out to be very simple, including the 1X's tables, color mixtures (such as yellow and blue make green), and puppetry. In the aftermath, Arthur and his friends proved her teaching skills were way too childish for everyone in the third grade (the Brain had the strongest opinions), and her brother finally returned the next day