Mrs. Smithers is Waylon Smithers, Jr.'s mother and Waylon Smithers, Sr.'s wife.
History
When Mr. Burns asks Smithers what he did over the weekend, he says that he caught up on his laundry and wrote a letter to his mother.[1]
In Moho House, Smithers brings a box of earrings and says to Homer that it was going to be a birthday present for his mother's 81st birthday, but asks him if he can give it to Marge in order to reconcile with her. Homer agrees, but when he tries to give it to Marge, she cries and leaves. Later, Marge finds out that the gift is not from Homer, but in order to hide the secret that the gift is for Mrs. Smithers, Homer asks Marge if she can at least open it so he can find out what it is, and says that he got the best gift he ever got her in his life, but Marge groans in annoyance when she finds out that the card says that it's for a woman on her 81st birthday (she's only 37 years old and isn't 81 like Mrs. Smithers is). Later, during the photo slideshow at the end of the third act, Mrs. Smithers makes her very first on-screen appearance, looking excited to open her gift when Smithers arrives and gives it to her. This episode is also Mrs. Smithers' first ever on-screen appearance in the show after being off-screen for 24 seasons.
In "Bart's Not Dead", she appears in Bart's daydream where he throws himself overboard.
Appearances
Episode – "Homer Defined" (mentioned)
Episode – "Moho House" (on-screen debut)- Episode – "Bart's Not Dead" (in Bart's dream)