- "A West Coast chain of 'never frozen, often microwaved burgers' served with a side of right-wing values, religious fundamentalism, and belief that everything was better before the Voting Rights Act."
- ― Description at LCN.com.
Its taglines are "Once It Pings, Eat Like Kings" and "Food from when we were morally superior". The latter refers to the restaurant's "atomic age" theme, as seen in their television advertisements. The atomic age (the late 1940s to mid 1960s) in the United States was characterized by strict social mores and patriotism. The company has 2 mascots named "Ray" and "May" who appear to be yellow blobs. Their taglines can be seen on the delivery trucks around Los Santos. The chain is based on In-N-Out Burger. Its main stock competitor is Burger Shot, while its other competitors stand as Cluckin Bell, Pizza This and Taco Bomb.
Their menu includes:
- The Triple Burger.
- The 10-slices of Bacon-Triple Cheese Melt.
- Extra Creamy Jumbo Shake.
- Footlong Chili Dog.
- French Fries.
- Chicken Liver Surprise.
Female Imaging Voice: "You do everything in your car - from talking to friends to watching a movie to turning tricks with a coworker, so why should you get out of your car to eat? At Up-n-Atom, we're from a time when America didn't worry about global warming, cholesterol, or who could vote. Drive into Up-n-Atom today! Up-n-Atom: Food from when we were morally superior."
Visible in pictures and trailers.
- Up-n-Atom is based on the Western hamburger chain In-N-Out Burger, with the the name being a pun on the phrase "up and at 'em".
- The tagline refers to Burger King, which is already parodied as Burger Shot. The yellow curve up over the Up n Atom name is reminiscent of both the In-N-Out logo and McDonald's "golden arches".
- In the TV commercials, some footage from L.A. Noire, in black and white mode, is used for the stock footage from 1950.
- The description of "served with a side of religious fundamentalism" is a reference to In-N-Out placing Bible verses on the bottom of cups and burger wrappers.
- This could also be referring to Chick-fil-A, a chicken fast food chain which was the subject of controversy after it was revealed that it had donated money to religious fundamentalist and anti-LGBT groups.
- When nearing the base of the rocket statue at the Procopio location, a Geiger counter can be heard with the clicks increasing as you move closer.