Revealing mistake: When Mrs. Slocombe's cat is supposed to be under the hat and "eats" the clockwork mouse, it is clear that it's a machine. This is most obvious when the hat spits out the mouse and slightly rises up in the front, which shows the wheels.
Miss Brahms: I think Mr. Rumbold should dress up as something. Mrs. Slocombe: Yes. Wasn't Frankenstein a German? Miss Brahms: That's right. With his nuts in his neck. [Makes twisting motions with her fingers near her neck.] Like that. Mr. Rumbold: I wouldn't be able to take part, of course, in case I was summoned to a board meeting. But I see no reason why Captain Peacock shouldn't participate. Captain Peacock: I can think of lots of reason why I shouldn't participate. Somebody has to have authority over the floor and these clothes that I wear symbolize that authority. Mr Lucas: Why don't you dress up as Hitler?
Question: Captain Peacock explained the real reason why he and Miss Hazelwood were late for work but, why did they both decide to hide the truth and make up a story as to why they were late? Why not just come right out and admit it? If they had, it would have been excusable.