Black Swan

The Black Swan is Melissa Hastings, Revealed in Episode Birds of a Feather ( Exposed ) The Black Swan is a character who first appears in "UnmAsked." Spencer finds the sketches for Black Swan's costume in A's lair, and Aria, Emily, and Hanna spot her at the Masquerade Ball. Her identity is unknown, and will be a mystery for Season 3. Before Mona disclosed to Spencer that she was "A," Spencer, Hanna, Emily, and Aria believed Black Swan may have been "A."

Black Swan is seen talking to Lucas and Jenna at the Masquerade Ball. When the Liars try to confront her she runs away from them.

Physical Appearance
Black Swan has dark hair, fair skin, and is described by Hanna as being tall and having a size two frame. She is seen wearing a costume similar to that of Odile in the ballet "Swan Lake." She wears a mask, which conceals her identity.

Suspects of Being Black Swan
Some suspects of being Black Swan due to physical appearance are:
 * Ashley Marin
 * Alison DiLaurentis/Vivian Darkbloom
 * Jackie Molina
 * Courtney DiLaurentis
 * Kate Randall
 * Melissa Hastings (Since baby bump was fake)
 * A student from Rosewood High ( maybe the mystery girl who was seen talking to Lucas in the first episode of season 3 )
 * A new character

Who Couldn't Be Black Swan

 * Jenna Marshall (Seen talking to Black Swan)
 * Maya St. Germain (Dead)
 * Aria Montgomery (Seen looking & running after The Black Swan)
 * Hanna Marin (Seen looking & running after The Black Swan)
 * Spencer Hastings (Was in A's Lair along with Mona Vanderwall)
 * Emily Fields (Seen looking & running after The Black Swan)
 * Mona Vanderwall (Was in A's Lair along with Spencer Hastings)

Trivia

 * Marlene King revealed via Twitter that the Black Swan's identity will be revealed in Birds of a Feather.