Little Mo first arrived on
Albert Square on 18 September 2000, along with her family: father
Charlie (
Derek Martin), grandmother
Big Mo (
Laila Morse) and sisters
Lynne (
Elaine Lordan),
Kat (
Jessie Wallace) and
Zoe (
Michelle Ryan), although Zoe is later revealed to be Kat's secret daughter following a family argument. They are also accompanied by Lynne's boyfriend
Garry Hobbs (
Ricky Groves) and later joined by Little Mo's estranged husband
Trevor Morgan (
Alex Ferns), a handyman who surprises Little Mo with his arrival just days before they celebrate Christmas that year. It soon becomes clear that their marriage had previously been troubled, due to Trevor being physically and mentally abusive towards her as a result of his severe mood swings and violent temper. This is further evident when Little Mo tries to leave her husband, but he deceives her into staying with him and proceeds to isolates his wife from her family – who despise Trevor due to his abusive nature. She always forgives him and even agrees to start a family. However, when he rapes her after she buys a hat to wear to Lynne's wedding which he has forbidden her from attending, she realizes she cannot bring a child into such an environment and goes back on the contraceptive pill. She finally leaves Trevor when she discovers he had deleted a message from Zoe, who has run away from home. Eventually, Little Mo attacks Trevor, hitting him with an iron when he attacks her. She goes home thinking he is dead, but when she and her sisters return to the scene, he is gone. Little Mo is prosecuted and found guilty of attempted murder but is released after Trevor does a deal with the Slaters: he will not give evidence against Little Mo, if Kat does not press charges against him for assaulting her. After Little Mo moves out and has to divorce Trevor, he terrorises her and takes her and
Sean, his son with
Donna Andrews (Paula Jennings), hostage in the Slater home, which catches fire. Fireman
Tom Banks (
Colm Ó Maonlaí) saves Little Mo and Sean. He goes back for Trevor but the fire explodes a can of petrol. Tom and Trevor die in the explosion, ending his reign of terror.
Billy Mitchell (
Perry Fenwick) and Little Mo bond over their respective abusive pasts. They become friends while Little Mo is married to Trevor and start dating after she is released from prison. Billy reveals his feelings during Trevor's trial when Mo admits that part of her reason for staying with Trevor was that he was the only man who ever noticed her that way. Trevor does his best to wreck things but Billy proposes by spelling out "MARRY ME" in alphabet macaroni and she accepts. After Trevor's comeuppance demise, the pair marry on Christmas Day 2002. (2001) Late one night shortly before their first wedding anniversary, Little Mo is raped by her crossword buddy,
Graham Foster (
Alex McSweeney), in
The Queen Victoria public house. When she tells her family, Charlie attacks Graham. Little Mo is tested for STIs after reporting him to the police. All the tests come back negative except one: she is pregnant. The Slaters and Billy are shocked and disgusted when she refuses to have a termination, claiming the baby is innocent of its father's crimes, so she and Billy separate. She leaves the Square, returning for Graham's trial. She tells Billy she named her son
Frederick William Mitchell, wanting to name him after good men. She and Billy reconcile after Graham's conviction, but later leaves him again after he tells her that he cannot accept Freddie as his son, because he is Graham's. Little Mo and Freddie move back in with her family. She and brother-in-law
Alfie Moon (
Shane Richie) become much closer following their respective separations but they end things when Mo learns Alfie is dating Kat behind her back. Alfie and Kat reconcile and leave the Square. Around February 2006, Little Mo is seen struggling to cope with Freddie's constant crying but refuses to medicate him for his teething, so she has trouble getting him to sleep. Freddie gets a head injury in a fight with
Bobby Beale (Kevin Curran) so a health visitor visits the Slaters. Little Mo is extremely hostile, seeing this as a questioning of her parenting ability. She constantly takes Freddie to see
general practitioner,
Oliver Cousins (
Tom Ellis), who moves her to another GP's patient list because he is interested in her romantically. They start dating in April 2006. Following her divorce, Little Mo and Oliver plan a night away in
Brighton, but after a car crash caused by
Deano Wicks (
Matt Di Angelo) and
Carly Wicks (
Kellie Shirley), she gets cold feet, telling Oliver that she cannot leave Freddie. On her return, she finds him unconscious. Freddie is rushed to hospital, where doctors find another head injury, and
Social Services suspect Little Mo. Thinking back, Little Mo realises
Ben Mitchell (Charlie Jones) is responsible. She confronts him and shakes him violently when he denies hurting him. Little Mo tries telling people that Ben caused Freddie's injury but no one believes her, not even her own father. Charlie soon realises his mistake and begs her forgiveness for doubting her. After extensive tests, the doctors discover Freddie has a low platelet count due to an infection, meaning that any minor injury can cause serious complications as his blood does not clot properly. Little Mo is cleared by the authorities, but local residents think she is responsible. Knowing she will always be suspected, Little Mo decides to leave. Feeling guilty, Ben finally tells his father
Phil Mitchell (
Steve McFadden) that he had hit Freddie, as Freddie pulled at his hearing aid. Little Mo is not sure what to do, but decides not to tell the authorities. Phil threatens Little Mo but she tells him she is quite capable of deciding for herself. Oliver suggests she report Ben but she refuses, leading to a nasty scene in the pub when
Peggy Mitchell (
Barbara Windsor) calls Little Mo a child beater. Oliver defends Little Mo and tells everyone that Ben confessed to Phil and Little Mo, but Little Mo is angry that he did not respect her decision. When Little Mo's cousin
Stacey (
Lacey Turner) spots a romantic spark between Oliver and resident
Dawn Swann (
Kara Tointon), she tells Little Mo, resulting in a showdown between Little Mo and Oliver in the square. During a scuffle, Little Mo pushes Oliver to the ground, and in response, he ends their relationship. As Little Mo prepares to leave for
Barnstaple, Oliver realises that he still loves her, and decides to ask her to go with him to
Leeds instead. He runs to the tube station and tries to convince her to join him. However, Little Mo rejects him, saying that all her life she had done just what she was told by somebody else and now she finally wants to break away from being "Little Mo." She gives him one last kiss, telling him she will keep in touch and visit him in Leeds. She leaves with Freddie on 26 May 2006, and Oliver leaves for Leeds the same day. In January 2016, Little Mo attends her father Charlie's funeral off-screen, and avoids Kat, along with their other sisters. In September 2022, a grown-up Freddie (now played by
Bobby Brazier), returns to Walford believing that Billy is his father. Billy goes along with Freddie's assumptions to spare him from heartache, until Billy's ex-wife
Honey Mitchell (
Emma Barton) phones Little Mo and urges her to tell Freddie the truth. Freddie is upset when Phil tells him that Billy is not his father. In August 2023, Freddie visits Little Mo off-screen after learning the truth about Graham and how the incident with her led to his birth. He confronts her for not telling him, resulting in a row between them. Little Mo is left devastated by the revelation that Freddie knows the truth about his father. Kat and
Jean Slater (
Gillian Wright) later visit her in Barnstaple to comfort her. ==Reception==