Lisa Ratburn

Lisa Ratburn is the mother of Arthur's third grade teacher Nigel Ratburn and his sister Rodentia Ratburn. She was only seen in Arthur's imagination of Mr. Ratburn as an infant. She referred to him as "Emil", but the teacher's given name was changed to "Nigel" in subsequent seasons. Although she hasn't actually been shown in the series, it is likely that she is currently middle-aged, since her son is a young teacher.