"Listen, Larry. We've got to load up all these onions in the bags as soon as possible." Then Larry considered whether he should clarify which ones were onions. He didn't want to look stupid so he just nodded his head and said OK. Six hours later they had a truckload of corn labeled as onions. "Larry, if you weren't my son in law I'd have you fired!"
This is when the farmer has to give an apologetic phone call to the store he's delivering to. "Sorry, but I've got more corn in onion bags for you." / "Are you kidding me? Just fire that idiot." / "I can't. My daughter loves him. Can you take them, just this one last time?" / "Fine... but this is it. No more corn in onion bags." And that, my friends, is where the phrase "no more corn in onion bags" comes from. Oh, wait. That's not a phrase? OK.