M.I.9 at one point worked with S.C.A.B 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".
- M.I.4 ("The Visit") - operates prisons
- M.I.9 (all episodes) - recruits teenage spies
- M.I.16 ("The League of Mata Hari") - unknown
- M.I.17 ("Vote SKUL") - currently guards HM Treasury
- M.I.19 ("The League of Mata Hari") - unknown
- M.I.25 ("The Wasp") - recruits teenage spies
- M.I.38 ("Skuldiggery") - archaeological department
- Abergavenny Smith
- Amber Bayes
- Edward Dixon Halliday
- Frank London
- Hamish Campbell (double agent)
- Hyperia Von Hades (ex-KORPS)
- James Blond
- Lenny Bicknall
- Mike Stern (double agent)
- Stella Knight
- 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 M.I.5 and M.I.6 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. M.I.9 was a real section, and M.I.5 and M.I.6 allowed the use of the name 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 N.O.S.E for short, similarly to how all of KORPS's divisions are named after body parts.