|Hair color||Dark brown|
|Family||Mr. Lancaster (husband)|
|Cartoon debut||"Arthur and the Real Mr. Ratburn"|
The librarian also appeared in "Meek for a Week," where she was shown as a resident of Westboro Apartments. She is seen as one of the residents who come to the roof to complain about Francine's loud drumming. In this appearance, she is in her pajamas.
She has a speaking role in "Arthur Makes a Movie" where she was locked out of the library's computer network system. Neither she nor Miss Turner could regain control because The Brain accidentally hacked into the system, which included access to the electrical circuitry.
- 102a. "Arthur and the Real Mr. Ratburn"
- 104b. "Arthur's Lost Library Book"
- 117a. "Meek for a Week"
- 204a. "Arthur Makes a Movie"
- 214a. "Sue Ellen's Lost Diary"
- "Arthur and the Haunted Tree House" (First identified as Mrs. Lancaster)
- She bears a resemblance to Becky.
- It is not known if she is related to 4th Grade Female Aardvark, but can easily be confused with her.
- Mrs. Lancaster does not seem to appear in Arthur's Almost Live Not Real Music Festival, but rather 4th Grade Female Aardvark does in similar clothing.