These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ensemble Darkhorse: Charlie Fairhead, who went from playing hockey in the corridors to becoming, by Word of God, the show's most important character.
Kath◊, a blonde nurse, whose Fandom is surprising considering she's an incidental character, only ever referenced by name, but not given any plotlines.
The blonde woman (played by an extra) who always appears in scenes alongside Ruth, Jay, Yuki and May. Not given a name, but sometimes referred to as "Claire". Rarely speaks. Also considered Fanservice by some. "Claire" mainly appears in scenes where Ruth and Jay are present.
A blonde nurse with slight purplish tones in her hair who is an extra. (Appears a lot more in recent episodes)
Kojo, a dark-skinned nurse. He's particularly liked by the ladies...
From the older episodes, Oscar the porter, who had a huge fandom.
More recently, Jill, a nurse who has no speaking part, but for some reason, a proper fandom.
Reverse Funny Aneurysm: Charlie and Baz's Ross-and-Rachel like relationship is compounded by having Baz briefly date a posh bloke called Charles for one episode. Charlie suggesting that they be "friends who sleep together sometimes" could also be likenened to the episode where Monica and Richard try to be friends.
Unfortunate Implications: The end of the Bex rape storyline in series 19. The culmination of Toby's exit storyline in series 23, which suggested that in the world of Holby, sleeping with a man automatically makes you gay (one character actually says as much without a hint of irony).
What an Idiot: Guppy snorting some heroin he stole from a patient because he thought it was cocaine.