M.I.9 at one point worked with SCAB (Section for Cybernetics And Bionics) for Operation Looking Glass.
As seen in "One Flew Over the Budgie's Cage", Frank London was awarded the M.I.9 medal for bravery. It is revealed that a Code Zero refers to worst case scenarios. The medal is also seen in "Return of the Dark Wizard". Both Tom Tupper and Dan Morgan were awarded the medal in the "Return of the Dark Wizard".
- MI4 ("The Visit") - operates prisons
- MI9 (all episodes) - teenage spy team
- MI16 ("The League of Mata Hari") - unknown
- MI17 ("Vote SKUL") - guards the Royal Treasury
- MI19 ("The League of Mata Hari") - unknown
- MI25 ("The Wasp") - teenage spy team
- MI38 ("SKULdiggery") - archaeological department
- Abergavenny Smith
- Amber Bayes
- Edward Dixon-Halliday
- Frank London
- George Bland ("One Flew Over the Budgie's Cage")
- Hamish Campbell (KORPS double agent)
- Horatio Stark (Chief Agent)
- Hyperia Von Hades (ex-KORPS, dead)
- Jade Dixon-Halliday (ex-M.I.9, SKUL)
- James Blonde ("The Others")
- Jemima Thursday ("Old School")
- Lenny Bicknall
- Mike Stern (KORPS double agent)
- Stella Knight (Chief Agent)
- The fictional Directorate of Military Intelligence sections in M.I. High. The names stand for: Military Intelligence, Section "X". Some names were used for real sections that are now nonexistent. Both of the only existent real life divisions of MI5 and MI6 have been mentioned in this fictional world, but are rarely referenced due to M.I.9 being the main security service in the TV series. MI9 was a real section, and MI5 and MI6 allowed the use of the MI9 name stylised as M.I.9 in the series due to their refusal to real names being used.
- The real MI9 was only active during WWII and specialized in aiding resistance fighters in enemy occupied territory and recovering Allied troops who found themselves behind enemy lines. They also sent gadgets to help prisoners of war escape such as compasses that were hidden inside pens or tunic buttons and maps disguised as silk handkerchiefs. All these gadgets were sent as aid parcels from fake charities.
- During, "Forever Young", the "National Organisation for Scientific Extrapolation" was seen; it was called NOSE for short, similarly to how all of KORPS's divisions are named after body parts.