I stopped at a local parts store (name redacted to protect the incompetent) a few years back for spark plugs. Specifically, I stopped for NGK BR7EF spark plugs, which were my plug of choice for my turbocharged LS1/RX7.

I went up to the counter and had the following conversation:

“Hi, I need some spark plugs.”
“Ok, what vehicle? Year/make/model, please.”
“Actually I have a part number, NGK BR7EF, your manager here keeps them in stock for me, since I use them a lot.”
“Well I need the vehicle to identify them.”
“No, you don’t, I can see them behind you on the shelf, that box, the one with my name on it, that’s the plugs, I need 8 of them.”
“Well I need a vehicle.”
“Okay, it’s a 2000 Corvette.”
“That’s the wrong plug for a 2000 Corvette.”
“No, it’s not, it’s just 2 heat ranges colder than stock.”
“That won’t work correctly, the computer says so.”
“Does the computer say what the plug will do if I pull the engine out of that car, forge the internals, change the compression ratio, port the heads, turbocharge it and put it in an RX7?!?!?”
“Well, no.”
“Okay, can I either have my plugs or your manager?”

17 dollars later and I had spark plugs. I started ordering them for delivery after that day.