I've had a few customers like this, but the most memorable one so far happened about 3 months ago.
So one of the sales associates calls back to the bay, asks me if i've got time for a deck and speaker install in a '04 SRT-4. I say sure, bring it on, I'll use whatever productivity I can get. Sales guy brings back the deck and speakers and sets them on my work bench while I'm pulling the kit, harness and antenna adapter, so I don't even notice that he brings me a set of Pioneer 6x8's until the customer gets there. Well, their 2004 SRT-4 turns out to be a 2003 base model neon with an SRT wing. Customer pulls up (right over top of the bright yellow 'NO PARKING' that's been painted onto the pavment) and the frighteningly large woman that got out says "I'm here for an appointment, now I just picked up this car today so you better not mess it up!" I smile cuz I know at this point it's going to be interesting. And it did;
Large Woman: "I need the deck installed and the speakers too, but I think the sales guy was confused"
Me: "How so?"
LW: "I think he thought that I wanted you to pull out my old back speakers and put new ones in."
Me: "Ya, that's normally where they go."
LW: "Well I don't want you to, I want to have six speakers."
Me: "Ok, well let me take a look at your car and we'll see what we can do" After seeing the 6x8's that she's selected "Well I can do a set of 6x9's on the rear deck , but with the way the third brake light sits, the boxes will be partially covering the factory speakers that you said you wanted to keep, which will reduce the overall sound quality. Also, the speakers that you selected are designed for Ford and Mazda vehicles, and if I were to put them into the boxes that we'd need, there would be a gap and you'd have pretty poor sound quality"
LW: (Turning to the weezly looking man she brought with her) "What is he talking about boxes for, I just want them there." (Turning to me and pointing at the rear deck) I just want them left out, why do I need boxes?"
Me: "Uh, I don't think I can do that."
LW: "Why not, my dad did it in my other Neon. You just run the wires through and it's done."
Me: "Miss, this is a proffessional shop and I'm a proffessional installer, and we've adopted the thinking here that you're only as good as your worst install. If I were to just leave the speakers chillin' on the rear deck, that would be BY FAR my worst install ever. Not only is it sub-par work, but it's a huge liability for me and my shop. If I were to leave them out, the first time you have to step on the brakes hard, they're going to come flying into the back of your head, and then you're going to come to me with a lawsuite and I'll lose my job. So I'm sorry, but either I do the job right or I don't to it at all."
Ended up just doing the deck install, sometimes I wonder what goes through people's heads.