Tell Me Everything initially centres on Jonny (Eden H Davies), whose mental health problems come into greater focus following a family tragedy, but also stars Spike Fearn, Lauryn Ajufo, Callina Liang, Tessa Lucille and Carla Woodcock as part of a greater ensemble; the production team stated that during the casting process, they focused on casting young and rising actors.

His best friends Louis (Spike Fearn) and Neve (Lauryn Ajufo) don't know how depressed he is as they are also undergoing their own personal difficulties as they enter college, which are explored with new students Regan (Tessa Lucille) and Zia (Carla Woodcock).

The series is written by creator O'Sullivan, Yemi Oyefuwa, Kat Sadler and Cameron Loxdale, and is directed by Richard Senior and Marley Morrison.

Heather Fallon of Broadcast commented that the "subject of mental health is at the very heart of Tell Me Everything, which weaves O'Sullivan's own experience of adolescent grief and depression with the frequent references that were made in the teen discussion groups".

Executive producer Campbell added that Noho "also sought out insights from the mental health charity Mind, as well as working closely with the BFI, which supported the drama via the Young Audiences Content Fund".

[10] The depiction of mental health, combined with the implementation of comedy, was something Campbell commented was their "biggest creative challenge", on the difficulty of balancing it right;[10] O'Sullivan said including humour was a key part of the series, as he had "always needed to search out the shards of light among the darkness, for my own sanity as much as anything else.

Campbell commented that the setting of the show was also of significance, such as in their attempts to distinguish Tell Me Everything from other similar content from abroad, in that "[t]hat suburbia is very recognisable for UK teens", and "the whole series has a very British sensibility.

"[12] Wulff-Cochrane said "part of the joy" of the show is its Welwyn Garden City setting, describing it as an "'everyplace' that represents the quirky oddness of this nation", and that "[w]ith its slightly suburban landscape it felt like a truthful representation of what it feels like to be a teenager in this country.

Emma Saunders, who interviewed O'Sullivan, Davies and Ajufo for BBC News said the drama was "refreshing" in how it "refuses to gloss over the tedium of depression and anxiety, zoning in on the panic attacks, insomnia and self-doubt that are often part of these conditions"; Davies expanded on this, saying "[s]ometimes, when we talk about mental health as a theme, it's in danger of being glamorised... in a way that's appeasing to people" and "[w]hat we did was create something that's ugly and jagged.

[16] Liang said this all "broke the ice", and the cast members "quickly became good friends which was amazing because every day on set, it didn't even feel like we were working.

"[17] Woodcock praised this type of rehearsal that O'Sullivan and director Richard Senior allowed prior to filming, commenting that "[i]t kind of felt like we were workshopping it, and really playing around with the scenes, which is quite rare these days".

[16] When the series was announced, the stars were billed to be Eden H Davies, Spike Fearn, Lauryn Ajufo, Callina Liang, Tessa Lucille and Carla Woodcock.

[8] Filming began in August 2021 and continued into the early autumn,[18][19] mainly in Welwyn Garden City, with one scene in the first episode shot in Letchworth.

"[20] Ajufo described her willingness to take part in the series, saying that she had "always wanted to do a teen drama", growing up watching many American ones, and "so it was a no-brainer that this was something [she'd] be interested in."

She detailed how cast members' own experiences with issues and topics that were presented within the series helped them prepare to depict them through their characters - with "a lot of discussions amongst ourselves with the cast and Mark [O'Sullivan,] the writer" - incorporating and "reflect[ing] on scenarios you or someone you know has been in ... into your performance", and how it was "super important for these matters to be seen from the perspective of a teen because self-doubt, trying drugs and drinking mostly start very young therefore it's best to have these discussions now rather than later".

She mentioned working with Zainab Jaye, the show's hair and makeup designer, which entailed "[c]reating different hairstyles and playing with colours [and] was just such a great experience.

It was reported that the series will feature a near-complete cast refresh - with the addition of cast members Nethra Tilakumara as Naisha, George Hawkins as Dylan, Sophie Ablett as Ella and Daisy Jacob as Bex, Levi Mattey as Josh, Ammar Duffus as Luke, and Dylan Brady as Tommy - as Eden H Davies' character of Jonny "move[s] to a new town as he continues his journey of recovery".

Comparing it to such dramas, Loffhagen noted the show "manages to retain the charm of these British teen classics while leaving behind the casual sexism and homophobia that make some of them an uncomfortable watch today, incorporating in their place same sex relationships and a diverse cast in a refreshing and natural way."

She went further, saying the series is "[b]eautifully shot and perfectly paced", praising the "pitch perfect casting [and] stellar script", with "Davies deliver[ing] a masterclass ... expertly flitting between grief, angst and ecstasy with the skill and honesty of seasoned professional," and that "[w]hile there are a few clumsy moments, Tell Me Everything does an excellent job of tapping into the truisms and sometimes mundanity of the teenage psyche, while also hinging around a genuinely captivating plot.

He notes that the other main characters are "all working within recognisable archetypes", but that underlying them are "strong dramatic instincts" that "seems worth watching and waiting to see how they play out".

[17] Madeline Reid of BRICKS Magazine was also complimentary, saying the show "is an unmistakable outcast" in comparison to other shows of similar ilk - naming Skins particularly - and "depicts an at-times alarmingly accurate account of British late teenagehood that feels timeless, combined with the painful reality of depression in the social media age", which "feels decidedly British, from its slang and dry humour to the hand-held shaky camera work.

While there are hints of Noughties indie-sleaze present, the show's contemporary sensitivity to stories spanning mental health, addiction, grief and queer identity cement it as a surprisingly realistic snapshot of life for young people in the 2020s."

Eden delivers a faultless performance as Jonny in his debut TV role, expertly flitting between grief, angst and ecstasy with ease", and that "[c]ombined, the cast's chemistry is evident, and when paired with witty scriptwriting and unexpected plot twists, the result is equal parts charming and comedic."

Reid also commented that it was "refreshing" that the series "refuses to gloss over the tedium of depression and anxiety, zoning in on the panic attacks, insomnia and isolation", and that "[u]nlike Skins, however, I doubt that this series will receive the same complaints for unrealistic depictions of teenage relationships, parties or drug use" as that "unlike its predecessors, there's a distinct difference in how Tell Me Everything treats its teenage characters and their traumas – rather than trying to shock audiences by uncovering the illegal antics of its central characters, the show expresses sympathy and support for its most vulnerable.

[34] On Twitter, creator and writer O'Sullivan responded mordaciously to her points, saying "Even if nothing else good ever happens, knowing that [the show] has triggered Julie Birchill will always be enough for me.

Only the second episode rated highly enough once catch-up outside of on-demand viewership was added to appear in the channel's top 50 programmes of the week, gaining slightly to 143,000.