The following is a list of characters that first appeared or will appear in the British Channel 4 soap opera Hollyoaks in 2012, by order of first appearance. All characters are introduced by the series' producer, Emma Smithwick. The first character to be announced was Ally Gorman; soon followed by Phoebe Jackson. While interviewed by Inside Soap, Smithwick announced that she planned to introduce more characters to expand the Kane family. The first to arrive was Martha Kane; soon followed by Lacey Kane – while Amy Downham joined the serial playing the role of Jen Gilmore. Later introductions include "bad boy" character Simon Walker and deaf teenager Dylan Shaw; while Maddie Morrison's father Ed and mother Elizabeth arrived. June saw the arrival of Walt played by former EastEnders actor Cliff Parisi. Liam Gilmore (James Farrar) began appearing from August, while Oscar Osborne was born prematurely to Darren and Nancy Osborne in October. Maxine Minniver, played by Nikki Sanderson, began appearing in November, as did Patrick and Sienna Blake, played by Jeremy Sheffield and Anna Passey respectively, as well as Jim McGinn played by Dan Tetsell and Brendan and Cheryl Brady's father, Seamus shortly followed.

Phoebe McQueen (also Jackson) played by Mandip Gill, debuted on 17 January 2012. Phoebe is introduced as a regular character. When Callum Kane (Laurie Duncan) visits the squat George Smith (Steven Roberts) is living in he meets Phoebe who also lives there. Phoebe wants Callum to stop interfering because his presence leaves her nervous. Gill told TV Times that her character is "streetwise" and unlike George she has been squatting for a long time. As Callum is George's friend she cannot trust him because "in her eyes anyone from the outside is trouble". Pheobe fears that Callum will report them and so does not want to go into care or lose George. Gill said that "he and her dog Thunder are all she has". This causes tension between Phoebe and George and he decides to move out. Gill said that Phoebe feels "guilty" because George is unwell and puts her feeling aside to ask Callum for help. Gill explained that "by this point, George is very ill and she knows it'd be on her conscience if anything happened to him."

In January 2012, the serial's producer Emma Smithwick said that she wanted to explore Ash (Holly Weston) and Callum Kane's (Laurie Duncan) backstories. She revealed that she planned to introduce "satellite" family members in the process. Martha will appear on a semi-regular basis. On the serial's official website, Martha is described as being "loveable but feisty, straight-talking and fun". Martha is more of a "liberal parent than a strict one". In November 2013 Digital Spy announced that the actress had left the show, her final episode aired 8 November 2013, Where Martha leaves to go live with her daughter Lacey and Sister.

Doctor Paul Browning, played by Joseph Thompson, debuted on-screen during the episode airing on 23 January 2012. Doctor Browning is described as having an "incredible capacity for Sleaze" and as a "man who needs to be in control and is not afraid to use underhand tactics to assert his power over the situation". Doctor Browning and Mercedes McQueen (Jennifer Metcalfe) begin a relationship, with Thompson explaining that the pair are "kindred spirits" with an "undeniable connection" who are "excited by how dangerous the other is". Doctor Browning becomes a suspect in the whodunit murder plot of Lynsey Nolan (Karen Hassan), who he is later revealed to have killed. For his role as Doctor Browning, Thompson was nominated in the "Newcomer" category at the 2013 National Television Awards. Laura Morgan of All About Soap felt that Doctor Browning is a "fairly obvious suspect" in the investigation for Lynsey's murder, while Inside Soap journalist Sarah was shocked at the revelation of Doctor Browning as Lynsey's killer, saying she had overlooked him as a suspect. Anthony D. Langford from AfterElton hoped that the character would not be revealed to be Lynsey's killer due to his enjoyment of Doctor Browning's relationship with Mercedes and their "blistering chemistry".

Ally Gorman, played by Daniel O'Connor, made his debut screen appearance on 31 January 2012. The character and O'Connor's casting was announced on 11 December 2011. O'Connor originally auditioned for a different role twice, before being asked to audition for the part of Ally. O'Connor was given the part and began filming his scenes three days later. The actor said of his casting: "I'm really excited about joining Hollyoaks, especially with its recent success. [...] I'm really looking forward to working with some of the show's most popular characters and talented actors." O'Connor signed up for an initial twelve episode stint, but his contract was extended and he became a regular cast member. In April 2012, O'Connor revealed that he would remain on the show "at least until the end of [2012]".

Deena Hardman, played by Sian Breckin, debuted on-screen during the episode airing on 31 January 2012 and remained until 13 March 2012. The character was announced while Daniel Kilkelly of Digital Spy interviewed Steven Roberts, who plays George Smith (Steven Roberts). Deena tries to help George and his friend Phoebe Jackson (Mandip Gill) who are living on the streets. Roberts said that Deena is "not all she seems – she's a very manipulative character and she hasn't got their best interests at heart." Deena and her husband, Graham Hardman (Steve Marsh) hold George and Phoebe against their will for human trafficking, but they escape. Hollyoaks later announced that the storyline had not finished and Deena and Graham would continue their scheme. Phoebe has been recaptured by Deena and she leads George into a trap for Deena. Gill told a writer from Inside Soap that George thought Phoebe was safe, but all the time she was locked up by Deena. She manipulates Phoebe into luring George back into her scheme, Gill added that "she'll hurt her dog if she doesn't retrieve George, that dog, Thunder, is all Phoebe has in the whole world." Hollyoaks also confirmed that they planned to air "harrowing scenes" once Deena recaptures George.

Phoebe and George ask Deena for money. She later finds George, giving him money to buy food. Deena invites George and Phoebe back to her house where she gives them food and shelter. She steals George's sim card and convinces them to stay another night. She tells sneaks out to meet Graham and informs him that she can get a good price for Phoebe and George. When Phoebe finds some photos of a lost homeless boy she knows, she realises that Deena has been exploiting children in a sex trade for money. When Deena realises that they have discovered the truth, she and Graham attempt to prevent them from leaving. When Phoebe escapes she goes after her; while Graham goes after George. They are later arrested for their crimes and George and Phoebe escape for good.

Lacey Kane played by Georgia Bourke debuted on-screen during the episode airing on 23 February 2012. In January 2012, the serial's producer Emma Smithwick tolod a columnist for Inside Soap that she wanted to explore Ash (Holly Weston) and Callum Kane's (Laurie Duncan) backstories. She revealed that she planned to introduce "satellite" family members in the process. The first to arrive was their mother, Martha Kane (Carli Norris). The character and Bourke's casting were officially announced on 14 February 2012. As the youngest of the Kane siblings, Lacey moves into family home following some time away. She was described as being "rarely short of something to say" and presents problems for house guest George Smith (Steven Roberts). Bourke told a reporter from Inside Soap that she found working on Hollyoaks "daunting" at first. She added that she found playing Lacey an enjoyable experience.