b997eee8_CCG___What_s_That_Inside_Joke___In_joke
[Card] TARDIS - Dog House [Exp.] MoW [Type] Ref [In-joke] 
The basis for this card is that in this era, K9 was frequently left aboard the TARDIS or otherwise disabled so he couldn't act as a deus ex machina.
Unauthorized Dr. Who CCG - What's That Inside Joke?
In-joke