I was commercial manager at autozone for awhile, but i would still help out in the front. One time a dude came in furious and threw a Duralast battery on the counter, exclaiming "Y'all sold me a DEAD BATTERY!" Needless to say, he was pissed, so I calmly went over and talked to him, and noticed the black plastic thing that covers the negative terminal was still on there. I asked, "Sir, did you take this off before installing the battery?"
He turned beet red and quickly apologized for freaking out, haha.