Callum was originally a comedic character who was jovial, dopey and "happy-go-lucky" and who wore shabby clothing and beanie hats.

Producers introduced Callum's brother, Stuart Highway (Ricky Champ); their relationship is initially portrayed as dark, but later becomes supportive.

Clay's portrayal of Callum has received a positive response from critics, with a Soaplife columnist describing him as "a welcome ray of sunshine in the bleak world of Albert Square", and Laura-Jayne Tyler of Inside Soap opining, "Square chiefs had clearly found a diamond in the rough with actor Tony Clay".

The following day, he offers his assistance in The Queen Vic as an apology, although annoys the Carters when he accidentally orders too much alcohol and breaks glasses.

[2] Tiffany Butcher (Maisie Smith) sets Callum up to spend time with her adoptive sister, Whitney Dean (Shona McGarty).

[4] They arrange to meet for a drink in The Queen Vic, and Whitney turns up in casual clothes and wearing no makeup but Callum has prepared for a date, giving her a rose and having candles.

Hoping to prove himself to Stuart, Callum confronts Fred Lewis (Malcolm Freeman), but lets him go when Mick threatens him with violence.

[20] When viewers suggested that the shooter could be Mick's son Lee Carter, with the role recast from actor Danny-Boy Hatchard to Clay, David Brown of the Radio Times doubted that this would be true.

[22] However, executive consultant John Yorke had announced in December 2017 that a new friend for Mick and a new interest for Whitney Dean (Shona McGarty) would be introduced in 2018.

[24] Callum departs in the episode broadcast in the United Kingdom on 16 February 2018, signalling the conclusion of Clay's contract.

[25] Claire Crick of Digital Spy pointed out that Callum was a plot device introduced only to support the Carter family's storylines, especially when Callum is revealed to be in ownership of an expensive ring, which he lets the Carters sell when they need money to save their home, a plot that Crick thought was "convenient".

[35] Clay told Duncan Lindsay of the Metro that Callum returns to Albert Square, the show's setting, because he views it as a home and opined that "he's ever really had a place to call home, this is where he feels loved by Whitney and I think he feels like this is his family, this is his world now and I think this is what brings him back.

"[31] On Mick and his wife, Linda Carter (Kellie Bright), offering Callum a room at their home, The Queen Victoria public house, as a thank you for helping them with their financial troubles, Clay explained that Callum wants to return to The Queen Vic and that after helping the Carters, he feels better about himself.

[31] Callum's return to EastEnders and secret was placed at number four in Digital Spy's "big soap moments you have to see this week".

[39] Callum's costume consists of "scruffy clothes and woolly headwear", mainly beanie hats, and he has a full fringe, which differs from Clay's appearance.

[46] Lindsay (Metro) reported that following the date, Callum continues to show his feelings for Whitney and starts "to win her round with his likeable personality.

[19] When Callum arranges a second date, a romantic meal on the roof of The Queen Vic, Clay said, "It's that kind of thing that you fall in love with.

[24] Tyler found Callum's location for the date amusing because in a recent storyline, Whitney's friend, Abi Branning (Lorna Fitzgerald), died after a fall from there.

[49] Following Callum's departure in February, Morgan hoped that producers planned to reintroduce the character by quitting his army job and returning to be in a relationship with Whitney.

[19] Ben Lee of Digital Spy thought that Callum's return would be good for Whitney as it suggested that their relationship would continue,[27] while Digital Spy's Laura Morgan thought that Callum would be the ideal partner for Whitney despite not matching the profile of her usual partner.

[33] In April 2018, Clay stated that he was open to Callum and Whitney marrying, adding that he would love to film a soap wedding.

[44] Mick's mother, Shirley Carter (Linda Henry), calls Callum "Halfwit" in the show due to his dim-witted personality.

[19] Clay told Kilkelly (Digital Spy) that there are several characters that he wants to star alongside, including Dot Branning (June Brown), the Slater family, Kim Fox-Hubbard (Tameka Empson) and Billy Mitchell (Perry Fenwick).

[52] Clay thought that Stuart's introduction supported Callum's presence on the show and found that it added a new "dynamic" to the character.

[53] After his first few episodes, Gary Gillatt, writing for Inside Soap, hoped that Callum would stay in the show because of his "tons of charisma".

[54] Reporters from Digital Spy liked the character, with Laura Morgan calling him "the kind of light comic relief we've all needed at the start of 2018.

"[43] Tyler of Inside Soap opined that Callum is "the real treasure to emerge from the bonkers plot [the heist storyline]".

[24] Rachel Lucas of What's on TV described Callum as the "unlikely villain [who] shot Mick Carter during Aidan Maguire's botched robbery!

[19] Clay told Tyler of Inside Soap that when a fan recognised him on the train, he did not know how to react, but explained that he was friendly and took a photo with her.

[24] For his portrayal of Callum, Clay was nominated for Best Soap Newcomer at the 2018 Digital Spy Reader Awards; he came in seventh place with 5.4% of the total votes.