One thing unique about ATL flights, unless they've changed recently, is that they're often downline catered. The outbound flight deadheads the food to ATL where it is unwrapped and served on the way back. It has happened many times in the past that the food was served on the wrong leg, leaving the true meal flight nothing to serve but pretzels. Back in the day, I may have even done it...ONCE. Because if you're the one who made the mistake and happen to be working the return leg, you're also the one who has to try and explain to the PAX why they don't have their expected meal. After that, you tend to make double sure you're serving the right meal on the right leg.