When Omega screams that his will is to destroy, his mask briefly flaps upward, revealing the actor's face.
Revealing Mistake: When the companions return to Earth through the pillar of smoke, their footsteps can still be heard after they supposedly disappear.
Revealing Mistakes: When the Doctors flee Omega's lair, they open the door, which is smooth on its outer surface. But outside shots reveal the door to be textured.
Brigadier: Sergeant Benton!
Brigadier: You and I had better make a full inventory of the HQ, make sure everything's back in place. All got to be accounted for, you know?
Benton: Well, excuse me sir, but if anything is missing, where do we say it's gone?
Briadier: Come along, Benton.
Second Doctor: Goodbye. It's been so nice to meet me.
Third Doctor: Yes, I see what you mean. And I hope I don't meet me again.
Second Doctor: Ah!
(The Second Doctor disappears.)
Dr. Tyler: Now I've seen it all!
Jo: Pity. He was so sweet.
Third Doctor: Yes, wasn't I?
Brigadier: Yes. Well, as far as I'm concerned Doctor, one of you is enough. More than enough.
Third Doctor [ of the second Doctor ]: Please ignore him, just ignore him. He's incorrigibly frivolous.
The Brigadier [ on the Doctors ]: Wonderful chap. Both of him.
The Brigadier [ regarding the first Doctor ]: That old chap…
Jo: Afraid so.
The Brigadier: Three of them. I didn't know when I was well off.
Second Doctor: If only I could find my recorder, I could play you a little something to pass the time.
Brigadier: We should be thankful for small mercies.
As a reward for his efforts, the Time Lords restore the Doctor's repressed memories on how to operate the TARDIS, and return its dematerialisation circuit, paving the way for the series to return to a more open format in the years to come.