Scream 3/Characters

Characters unique to Scream 3

Arc Welding: Revealed to be the person who put Billy and Stu up to murdering Maureen in the first place.
Big Bad: Of the third film.
Cain and Abel: He's Sid's half-brother from an affair Maureen had when she was living in L.A.
Child by Rape: Strongly implied.
Faking the Dead: Perhaps the most controversial case in the series.
Hollywood Nerd
The Man Behind the Man: He was the one who incited Billy to kill Maureen one year before the first movie.

Casting Couch: How she got the part of Sidney in Stab 3.
Death by Sex: She gets killed literally seconds after revealing that she had employed the Casting Couch to get the part of Sidney. Damn, do the rules strike fast!
Final Girl: She's playing one in Stab 3, and she's initially presented as such. She dies, though.
Foreshadowing: Averted. Early in the film, she wonders if it will turn out that her character, Sidney, is the killer in the third Stab movie (the cast only has partial scripts to prevent leaks). In the original script, she was one of the killers alongside Roman, but this was changed in the final draft.
The Ingenue: What she presents herself as. Actually, she's anything but that.
Red Herring
Suspiciously Similar Substitute: For Sidney.

Brainless Beauty: Partially subverted; she may acts as The Ditz, on occasion, but overall she comes off as sharp as her fellow actors. (Which is not saying much.)
Dawson Casting / Playing Gertrude: In-universe Sarah is a 35 year old actress playing a 21 year old character. In real life Jenny McCarthy was (then) 27.
Death by Irony
White Dwarf Starlet: She's afraid this will be her fate, and seems quite unsatisfied with the way her career's panning out: as it is, she'd love to get out of Stab 3.

Cash Cow Franchise: As the head of Sunshine Studios, he turned the Stab film series into this.
Executive Meddling: Along with other producers, he pointed out the violence in Stab 3 would upset the Moral Guardians.
Jerkass
Luke, I Am Your Father: He possibly was the father of Roman Bridger
Red Herring
Sacrificial Lion
Suspiciously Specific Denial: When asked about Maureen Prescott/Rina Reynolds, he claims he's employed too many actors to remember. Gale quickly points out nobody said she was an actress.