- Adaptational Personality Change: In the novel, Marcia is a brooding, pessimistic intellectual English girl. Unlike the other selves, she prefers writing to painting, but she certainly has interests, preferences, and a distinct personality outside her depression (there's even an amusing incident where Sybil learns that Marcia's been trying to make extra money by writing and selling brainless little pop tunes; Sybil is mortified that someone might think she's been writing such drivel, while Marcia's only interested in what sells). In the 1976 film, Marcia has no English accent and no apparent interests other than her desire to kill herself (and the others). In the 2007 remake, she's a painter with a strong Noo Yawk accent, a gruff, no-nonsense attitude, and no apparent depressive or suicidal urges at all. Weirdly, she's also coded as a lesbian, judging from her preference for masculine clothing, her habit of wearing her hair tucked into a cap, and her scoffing whenever Sybil or one of the other selves has a date with a man.
- Adaptational Nationality: Vicky between Real Life and all of the future adaptations. In Real Life, the Vicky alter claimed to be visiting from England, not France, and while her first name was still Victoria, her surname was not French. It's presumed that this was either a misguided attempt to conceal the real Sybil's identity still further or because it sounded more impressive and mysterious to suggest that a personality could be conversant in a foreign language that the host had never consciously learned.
- Related: In the book, Vanessa is also said to be English. In the 1976 film, she has no English accent. But in the 2007 version, she's English again.
- Science Marches On: In the film, DID (Dissociative Identity Disorder) is called "Multiple Personality Disorder". The name hadn't been used since the DSM-III and, like the name, a lot of the terminology and diagnostic criterion since the '70s and DSM-III had changed(the "alters" are called "personalities").
Trivia / Sybil