Rodentia Ratburn

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.

Rodentia was also seen at Mr. Ratburn's wedding in "Mr. Ratburn and the Special Someone."

Physical appearance
In her first appearance, Rodentia looked very much like her brother, except with short brown hair. She wore a cream-yellow shirt and a yellow vest, along with a skirt and high-heeled shoes. Like her brother, she wears shirts tucked in.

In Arthur, Buster and Francine's imaginations before they met her in the classroom, she had straighter hair and was wearing a headband and a feminine version of Mr. Ratburn's uniform.

Past life
Her appearances shown below are what she looked like in Arthur and his friends' imaginations before encountering who she really looks like, and their imaginations were completely sepia.

Personality
Rodentia is a fun-loving teacher with a sweet, high-pitched voice. She loves to teach, sing and play guitar, among other things, and gets along well with her students. However, her teaching curriculum is not considered challenging enough by Arthur and his third-grade classmates, suggesting that she may be more qualified to teach preschool or kindergarten. She didn't seem aware of the insufficient challenge she presented to Arthur's class, as she didn't increase the difficulty of the material much after Brain remarked how childish her lessons were. Still, she remains laid-back and optimistic.

Family

 * Nigel Ratburn: Rodentia is Mr. Ratburn's sister, and from what little has been seen of their relationship, they do seem to be close despite being very different. In Arthur's fantasies, they were sworn enemies, dedicated to outwitting each other in every field.
 * ex Husband: While little has been seen of Rodentia's family, it would appear that she’s married, as in the episode "Desk Wars" Mr. Ratburn learns that she just had a child; although in Arthur's Substitute Teacher Trouble, her pregnancy was unknown. However it’s revealed that they long since divorced in Mr. Ratburn and the Special Someone and Rodentia is planning to remarry someone else.
 * Child: Rodentia has at least one child as of the episode "Desk Wars". That day, Mr. Ratburn announced to the class that he had just become an uncle after having received a call from his sister.

Trivia

 * Her name, Rodentia, is a play on the fact that rats and many other small mammal species belong the the taxonomic order Rodentia.
 * When Arthur is flipping through channels in "Arthur Plays the Blues", her character model is reused as a famous concert pianist.
 * Rodentia is a lot like Miss Sweetwater and Mrs. Fink in which she does a lot of fun stuff rather than true teaching. In fact, they have the same teaching methods and both just happened to be playing "I Like Fudge" on the guitar at exactly the same time.
 * In the episode, "Desk Wars", it‘s revealed that she became a mother and she has given birth to her child, although her pregnancy was unknown in Episode 127B.