Mary-Kate Olsen is getting back to her roots.
No, not her blondish locks.
M-K will be guest starring on ABC's show Samantha Who? in the fall - tentatively skedded to appear in one ep.
Star Christina Applegate who plays titular Samantha will try and save a confused Olsen, a self-destructive bad girl.
The series premise is Applegate's character is an amnesiac trying to discover the mysteries of her life -- kind of like a chick-lit version of Memento but without the mayhem and just the comedic aspects of good-versus-evil.
M-K was last on Showtime's Weeds tormenting Silas.