- This article is about the character. For the guest star, see Mary-Kate Olsen.
| Mary-Kate Olsen
| Character Information
Mary-Kate Olsen is an American actress. She is the twin sister of Ashley Olsen.
Mary-Kate and Ashley Olsen read the audiobook version of The Harpooned Heart. When one of them would finish their part, they would tell their sister to take it from there.
Milhouse read the book Bye-Bye Boyfriend by Mary-Kate and Ashley. On the cover of the book, Mary-Kate and Ashley had left their boyfriends behind and were driving away. Milhouse said that sometimes he felt like the third Olsen twin since he had read all their books.