I have to admit, this week's Why it's there is my absolute favorite hidden detail about the Tower of Terror. I think it's so neat and well implamented that it's always been the first detail I point out to anyone I ride Tower of Terror with. When you get into the actual ride vehicle on the Tower of Terror, on the left side by the first row is a certificate for the elevator. This isn't just another bit of detail, but a reference to a classic Twilight Zone attraction.
The elevator permit is signed by "Cadwaller" and the story behind it is in the Twilight Zone episode "Escape Clause", there is a character in episode called Cadwaller, who is later revealed to be the Devil. So the elevator certificate is signed by the devil. How about some more Twilight Zone goodness, like the elevator permit number, "10259" , which refers to the first air date (10/02/1959) of the Twilight Zone, which is labeled “where is everyone”. Lastly, if you look at the date it was last inspected on October 19, 1939 that is exactly 13 days before lightning struck the tower, according to the backstory of the Tower of Terror attraction.