Before "Casualty@Holby City", the two shows had occasionally crossed-over storylines and cast members before. For example developing a romance between "Holby City" Ben Saunders (David Paisley) and "Casualty" Tony Vincent (Lee Warburton).
The first full crossover was made by "Casualty" executive producer Mervyn Watson, and "Holby City" McHale. Work on both shows had to be halted for two weeks to release cast members to appear in the special.
A second crossover was commissioned in 2005 as part of the BBC's DoNation season. This aimed to raise public awareness of organ donation and to decide to sign up to the Organ Donor Register. An interactive episode of "Casualty@Holby City" was one of the headlining shows of the season, allowing viewers to vote by phone to determine the outcome of a fictional organ donation.
The third "Casualty@Holby City" crossover aired in October 2005. The four-part storyline tackled the issue of youth violence, following the events of a turbulent A&E demonstration at an inner-city school.
Another crossover was ordered for Christmas 2005. Rather than dividing the episodes between the two series' crews as had previously been standard, this crossover operated as an entirely separate production, with Kyle producing and Paul Harrison directing.
In February 2010, another crossover occurred when "Casualty" Charlie Fairhead (Derek Thompson) was operated on by "Holby City" Elliot Hope after suffering a heart attack. The storyline was shown as "Casualty" and "Holby City" episodes, rather than under the "Casualty@Holby City" title.
"Casualty" series producer Oliver Kent commented that, while it is "fantastic" to be able to produce crossover episodes, they are logistically difficult, and it is unlikely that another "Casualty@Holby City" episode will be produced in the "foreseeable future".
In September 2010, "Holby City" nurse Donna Jackson (Jaye Jacobs) appeared in "Casualty", and Kent hopes that characters from the two shows will begin to crossover two or three times a year.
On 27 April 2006, the BBC announced "Holby Blue", a police procedural spin-off from "Holby City". It was created by Tony Jordan.
"Holby City" was moved to Thursdays for the duration of "HolbyBlue" first series, with the spin-off broadcast on Tuesday nights at 8 pm.
In 2008, a two-part crossover episode with "Holby City" was developed for the beginning of the show's second series. The episodes were written by McHale and Jordan. "Holby City" registrar Jac Naylor accused of murder.
Yorke compared the crossover to the American "CSI" franchise, in that: "You really believe it's a world."
The second series attracted 5.6 million viewers to its opening episode. By the end of May 2008 viewer numbers had fallen to 2.5 million.
In August 2008, the BBC announced that, due to lower ratings, "Holby Blue" would not be recommissioned for a third series.
In June 2002, cast members from "Holby City" and "Casualty" competed against the "EastEnders" cast for the first "Sport Relief" fundraiser, dubbed "Sport in the Square". The teams competed in events such as taxi pulling, melon tossing and a beer keg relay.
The competition was shown on BBC One, and the event raised £10 million.
In October 2003, BBC One aired a "Kenyon Confronts" documentary by "Panorama" reporter Paul Kenyon, investigating hospitals run by the Private Finance Initiative. He discovered many problems within the hospitals, which were dramatised by the "Holby City" cast in specially written scenes.
In March 2004, the documentary "Making It at Holby" was made as part of a BBC initiative to develop new acting talent. The documentary followed the casting process of "Holby City" and "Casualty", from the audition stages to the filming of the selected actors' first scenes.
In November 2006, the "Children in Need" charity telethon included a segment featuring the "Holby City" cast performing a comical version of "Hung Up" by Madonna.
In November 2007 "Children in Need" appeal again contained a musical performance from Holby City cast members. Sharon D Clarke, backed by Nadine Lewington, Rakie Ayola and Phoebe Thomas performed a soul version of Aretha Franklin's signature song, "Respect".
On 28 June 2008, "Holby City" stars competed against their "Casualty" counterparts in a special charity edition of BBC Two game-show "The Weakest Link".
In February 2010, "Holby City" and "Casualty" cast members performed a dance rendition of "Jai Ho" for "Let's Dance for Sport Relief".
"Holby City" has been compared to other medical dramas, often unfavourable.
In November 2002, John Whiston, then head of drama at Granada Television, accused the BBC of producing inferior "parodies" of ITV drama. He commented "With "Holby City" cloned out of "Casualty", the BBC has even ended up copying itself."
Paul Hoggart of "The Times" says that the differences between the two shows are "mild", calling "Holby City": ""Casualty" cute little sister".
Kevin Lygo, director of television at Channel 4, referred to "Holby City" as "sudsy drama", deeming it, "Casualty" and "HolbyBlue" "all decent programmes, but strikingly similar in many aspects of their tone and construction."
"Holby City" has been unfavourably compared with the American medical drama "ER". Television producer Paul Abbott has commented that although he watches "ER", he does not watch "Holby City" as: "it looks like you've crammed one hour's drama into 26 episodes."
In October 2009, former "Holby City" writer Peter Jukes wrote a critical piece for "Prospect" magazine, contrasting the show negatively with the standard of American television dramas. Jukes wrote that "Holby City" has become a soap opera, rather than a drama, and deemed the episodes he worked on "the most dispiriting experiences in [his] 25 years as a dramatist."
In August 2002, Paul Bolt, director of the Broadcasting Standards Commission criticised BBC programming as being "humdrum" and "formulaic", saying of "Holby City" and the police procedural "Mersey Beat": "One begins to wonder what really is the point of the BBC bringing this to us. Let's have something a bit different." Then head of BBC drama Jane Tranter responded that Bolt's examples were "highly selective" as well as "hugely patronising to the millions of viewers who enjoy popular dramas like "Holby City" – week in, week out". Young, who at the time held the position of head of drama serials, told "The Guardian": "Popular drama has always been singled out for criticism, but people are increasingly voting with their on-buttons."
At the 2003 Edinburgh International Television Festival, BSykB chief executive Tony Ball called for stricter restrictions on how the BBC spent licence payers' money, suggesting that "Holby City" be sold to the channel's commercial rivals, with the proceeds used to develop more original programming. The BBC refused Ball's suggestion, responding in a statement: "This speech clearly reflects BSkyB's view that programmes are merely a commodity to be bought and sold."
In 2003, former BBC host Sir Ludovic Kennedy complained that ethnic minorities were over-represented on television, prompting a BBC spokeswoman to explain that "Holby City" has more ethnic characters as it is set in an area where minorities account for up to 30% of the population. According to the 2001 census, the population of Bristol – which the city of Holby is loosely based upon – is 88% white and 12% ethnic minorities.