Factual error: In the Ascot racing scene, the actors' heads move from their left to right when the horses come to the winning line. From the stands at Ascot, the horses run clockwise around the track and would enter from right to left.
Factual error: Elvis and Ann Margaret take a trip in a helicopter over Hoover Dam and Lake Meade. They are flying in a small 2 seater copter with a bubble canopy and no doors. During the trip Elvis and Ann talk to each other without headphones or microphones in a normal tone of voice. In that type of helicopter, especially one with no doors, the sound would have been deafening and they wouldn't have heard each other even while screaming.
Factual error: The radio Walter uses on the island has no apparent power source; we never see either batteries or a hand-cranked generator.
Factual error: Ma Tatum, while bemoaning Pappy's misfortune, sits herself on a burlap bag marked "Mash". Mash, the basic component of moonshine, is a semi-liquid, and couldn't be stored in a burlap bag.