Keegan Baker (also Butcher-Baker) is a fictional character from the BBC soap opera EastEnders, played by Zack Morris. He first appeared in episode 5421, broadcast on 9 January 2017, transpiring to be a school friend of established character Shakil Kazemi (Shaheen Jafargholi). Morris began filming in November 2016 and Keegan was introduced to become prominent in storylines focusing with other teenage characters, namely Shakil, Bex Fowler (Jasmine Armfield), and Louise Mitchell (Tilly Keeper). Initially characterised as an arrogant and spiteful bully, Keegan's character became more sensitive and sympathetic throughout his time on the soap, particularly following the introduction of his family – the Taylors – in June 2017. During the family's announcement and promotion, it was kept secret that Keegan was their relative.

Keegan and Shakil became the focuses of a storyline about gang violence in 2018, which saw both characters be stabbed, resulting in Shakil's death. The storyline was considered as one of the most important in the show's history by executive producer John Yorke. In the aftermath of the stabbing, Keegan began a relationship with Tiffany Butcher (Maisie Smith), with the couple marrying in November 2019. Morris opined that despite their character's young ages, their attraction was genuine as they were bonded by both having to mature quickly. In February 2022, it was announced that Morris had left the soap to pursue other projects. The actor sang praises of his co-stars before Keegan and Tiffany departed in episode 6453, broadcast on 17 March 2022, being given a rare happy ending to their story. Keegan's character development and storylines often attracted critical praise during his run, with Morris securing several awards and nominations for his portrayal.

Keegan made his first appearance on 9 January 2017. Zack Morris's casting was announced by his theatre school D&B Academy of Performing Arts beforehand, which he still attended when he received the part, with the school promising that he would be "one to watch". He was introduced on a six-month contract as a friend of Shakil Kazemi (Shaheen Jafargholi). A show insider told the press Keegan would become more promenant in the show's storylines with the other teenage characters, namely Shakil, Bex Fowler (Jasmine Armfield), and Louise Mitchell (Tilly Keeper), and that he would continue "to cement his reputation as a troublemaker". Keeper revealed that herself and Morris had the same agent and knew each other for years prior to his casting. Morris reported that he was "having a ball" playing a villain like Keegan, and sang excitement about his new role, but described it as "daunting" to join EastEnders as: "EastEnders is a show that's been going on for so many years and it's such a big part of British television. But when you get there, everybody is so nice to work with – all of the directors and all of the cast. So it's a nice, easy place to settle in".

I was filming on the market on my first day. It was all a bit overwhelming to be honest, because of the fast pace. But you do get used to it, and it teaches you to be prepared from the off.

Morris disclosed that he began filming in November 2016, and that the audition process was "quite a while" before that. He explained his audition process for Keegan: "When I had my original audition, I didn't hear anything back for quite a while, so I actually assumed that I didn't get it. But after a few more weeks, I heard that I had another audition and it all worked out from there". After he was cast, Morris had Jamie Borthwick, who played Jay Brown, as a mentor on set, whom he praised for being "very wise for such a young guy" and for giving "great advice". Morris found it "nerve-wracking" to join the show, labelling the role of Keegan as "the biggest job" he had ever gained and found it enjoyable to play a villain, commenting "it's so much more fun", despite clarifying that he was "not like Keegan in real life". When asked if viewers would be able to warm up to Keegan, Morris responded: "That's something you'll have to keep watching to find out. As much as you guys don't know what's coming up, we don't know what's happening in the future either". The actor himself commented that he would "like" for Keegan to be deeper than it first appeared, but reiterated that he didn't know what would happen. After Keegan began receiving mixed reactions, Morris took it as a "positive" as "the viewers are buying that I'm evil, so I'm fine with that".

Upon his arrival, Keegan is in his mid teens. Daniel Kilkelly of Digital Spy billed Keegan as a "villain" and a "new bad boy" for the soap. When asked to describe Keegan, Morris called his character "cocky", "aggressive", and that he "thinks he's the leader of the pack". He added that Keegan "thinks he's a bit bigger than what he is", and concluded: "All in all, he's a bit of a dick, really". The actor hoped Keegan would eventually grow on people, but said there wouldn't be many "redeeming features" for his character. He added that a key trait of Keegan's is to "shock" people. Morris described Keegan as "boisterous", and noted that he knew people like Keegan during his own time at school, adding that people-watching often helped him represent people's characteristics. Morris detailed that during his own school years, he wasn't "extremely naughty" or "extremely good", finding himself identifying with his character's "cheekiness" and not his "bullying". The actor explained that Keegan has "a bad sense of humour", "finds the wrong things funny", and "has no sense of judgement". He compared Keegan to "a bull in a china shop" who "smashes through" his obstacles. Morris further described his character as "cheeky and obnoxious", detailing that Keegan "likes to be the leader of the pack". Morris explained that Keegan "has a very short fuse", and "doesn't back down".

Keegan has been described as a "nasty piece of work", a "teen tearaway", "disruptive", "volatile", and "tortured". Dainty noted that Keegan "has no respect for his elders, and generally just thinks he's a bit indestructible". Several critics have described Keegan as a "troublemaker" or "troublesome". Morris opined that Keegan wasn't the type to "redeem himself". Inside Soap's Allison Jones described Keegan as a "spiteful schoolboy" and a "terrible bully with a shocking lack of respect". Morris often explained his belief that Keegan's personality was born through "something in his past". The actor opined that he would get along with Keegan, finding some of his jokes funny, and adding that Keegan would back someone up "if [they] needed it". Throughout his time on the soap, it was often noted that Keegan's rough nature had softened. Duncan Lindsay of the Metro explained: "Keegan began his life in Walford as an odious character but he has been developed a lot since then and despite maintaining his edge, his deep love for his family and the root of his acting out have been explored more". Laura Morgan of Digital Spy described Keegan as a "reformed bad boy", adding that he had "proven that he's rather a sensitive, caring soul under all that bravado".

Morris disclosed that Keegan was introduced as an abrasive teenager to leave room for character development. Morris attributed Keegan's personality change to the introduction of his family and audiences learning more about him, explaining: "It's about understanding why he does the things that he does and says the things that he says. It's because of what his environment has been, and people might be able to relate to that". The actor has explained that a trait of Keegan's include struggling to control his emotions, explaining that: "He's not very good at showing emotion and keeps things under wraps. For Keegan it just bubbles up until he's about to erupt". When asked what advice he would give his character, Morris responded that he would tell Keegan to "think before [he] acts", adding that his character "needs to realise that every action has a consequence". Morris has also said Keegan is "not the type of person to ask for any help".