Classic Series

I don't know how many of you actually remember pi? But remembering this scene from the 5 Doctors is how I remember. To the point where I actually hear the actors voice in my head when I repeat it out loud.
I have been rebuilding some of the items from the original console room. Ok one of these things doesn't belong here. Can you guess which one?
Part of Gabriel Chases house from Seeds of DOOOOOOM!!
Watch where you step. Everything is designed to kill you!!
The Reactor Room again, but looking the other way this time.