Hey, It's That Guy!: A bit part in this comes as standard on every British actor's CV, and the has given parts to more later-established actors than any other in the history of British television, so there are a lot of these of many different calibres. There's...
I Am Not Spock: This applies to Michael French (aka Nick Jordan), Derek Thompson (aka Charlie Fairhead, who is probably the iconic character of the show), Will Sharpe (Yuki), Sunetra Sarker (Zoe) and the anonymous blonde actress who plays Kath (identity of actress is unknown for now).
Amy Wren, who appeared as Kelly Oswald in the episode The Enemy Within.
Keep Circulating the Tapes: Only Series 1-3 have been released on DVD to celebrate the show's twentieth anniversary with no plans for any more despite petitions.
Old Shame: Matt Bardock (aka Jeff Collier the paramedic)'s appearance as a youth responsible for arson back in 1993. That's in the fan's opinion anyway.
After dealing with the case of a private dancer who'd been unknowingly taking stimulants disguised as vitamin pills provided by the club owner, new-ish paramedic Tamsin reveals that she knew what was happening because she used to be a dancer working for the same club owner.
The Other Darrin: Seemed to be a thing with children of staff. Happened to Tally once, although in hindsight this was probably for the better. Louis is by far the worst offender, having been played by about four different actors.