I used to work at a mom and pop parts store, a total of more than twelve years there, busy place. Early on a Saturday morning I answer a call from someone looking for an alternator for his Olds Cutlass, look it up, yep we have it in stock. He said he was going to remove it and bring it with him later in the day. Late afternoon rolls around, the door opens and in walks a guy who is just filthy, clothes and all exposed skin everything is just grease and dirt covered. He is carrying an A/C compressor with hoses, and brackets still attached. Flops it down on the counter and said he called this morning for an alternator for his Cutlass.
I swear I did not laugh...................
Next bozo, comes in for a pan gasket for his Turbohydromatic 350 trans, I get the gasket without referring to the book and sent him on his way. A few hours later he returns with a grimy pan and the gasket screaming at me for giving him the wrong part. He included how pissed he was that I didn't even look it up, just grabbed it out of the drawer. I picked the gasket up and flipped it over, what do you know, now all of the bolt holes line up.
Third and my favorite. new pads for a mid 70's full size Ford, the D50 pads fit like 10 years of production. The customer is the father of a high school friend, he returns with the pads saying they are too thick. We went thru the usual questions, C clamp to push piston all the way back, cap off master cylinder, a yes to everything. He finally says he would bet me $50 I had given him the wrong pads. Upon arriving at his house and I find he had not removed the wedge and key but the entire caliper bracket from the spindle, I installed the new pads quickly. Told him to keep the money and tell his son I said hello, he returned to the store often after that, always waited for me to help him.