b997eee8_CCG___What_s_That_Inside_Joke___In_joke
[Card] Mawdryn Undead [Exp.] DoG [Type] Ref [In-joke] 
The link to Ian Chesterton is because the story was initially written for him, but the actor proved unavailable (which is why The Brigadier suddenly became a teacher).
Unauthorized Dr. Who CCG - What's That Inside Joke?
In-joke