Revealing mistake: During the "Red" number in the Emerald City, a large screen is supposedly telecasting from the walking camera focused on the dancers below. Watch closely and you'll see the dancers' movements do not coincide with the movements displayed on the screen.
Revealing mistake: While Billy and Eli are on the river, with Eli in the front and Billy in the background, pay attention to Eli's paddle. When it passes in front of Billy, you can see right through it to see Billy through the paddle. (00:56:25)
Revealing mistake: When Jake reactivates the old biplane at Daley's Airport and Wilson mounts it as it takes off to pursue Olympus, you can see the wires from which the skeletal plane is hanging. (01:29:20)
Revealing mistake: When Tony is stacking the wine barrels in Gannon's lab, you can see the wires pulling the last barrel up into the pyramid.