The War Games
"...cruel Martian invaders."
In the final episode of The War Games, the Second Doctor is put on trial by his own people-- the Time Lords. The charge: breaking the Time Lord law of strict non-interference in the affairs of other species.
In his defense the Doctor uses a "thought channel" to show the Time Lords some of the evil he has fought. On the screen a Quark, a Yeti, a Cyberman, a Dalek and an Ice Warrior appear.