I'm an MRI technician. A client came in for a scan, and we instructed her to take off her metal bracelet before her scan.

Client: This isn't metal - it's silver. 

Client: While I've got you here, would you mind formatting this pamphlet for me?

Me: I'm a WEB designer, not a print designer.

Client: Is there really a difference? 

Client: What the hell! You overcharged me!

Me: I sent an invoice for what we agreed on.

Client: Bulls***. I'm looking at a bill for over four thousand dollars and we agreed on $500. 

Me: Yeah, I sent an invoice for $500. 

Client: Well then what the hell am I looking at?

Turns out it was his credit card bill. 

Client: The site is in color... I didn't ask for that.

Me: Well, no, but it's in line with your branding. Is it wrong?

Client: It looks good, but I will NOT pay for the color. If it costs anymore, I want this site in Black and White - and don't you DARE try to charge me more. 

Client: Do you have Adobo Pictureshop? Or, what do you call it, Imp Design?

Client: I like the logo, but what's with the checkerboard pattern in the background?

Me: Oh, that's just how Photoshop indicates that it's a transparent layer.

Client: It's ugly. Get rid of it, and then I think it's good.

Client: So, for my site, I want a Google.

Me: A Google site? 

Client: No, like an entire Google. 

I wrote an ad campaign for a client targetting millennials back when that was a thing. It was personable and authentic, and a big success when we ran it. The client got loads and loads of clickthroughs and I even won a local ad award for it.

After the first week, though, when the campaign was already a big success:

Client: You know, you should really make your ads more professional. This was way too casual. Just a little tip for the future. 

I was flabbergasted. I'd just done a REALLY GOOD JOB and the client was still trying to give me career/life advice. Obviously he'd missed the point of the campaign, but IT WAS WORKING. You'd think he'd shut up at that point. 

I was working with a client who had, and I quote, "decades of experience working with designers" and "loved to keep up with new technology." 

Me: Would you mind sending me PNGs rather than JPGs? I could use the transparent background.

Client: What's a PNG? I've never heard of it. Is that a Photoshop thing or something?

Yeah, you're really up to date. 

Client: Quick question: we use Lenovo in the office. I noticed you're on Mac - will the files be compatible with our computers? 

Me: ...Yes.

Client: Phew! That's a relief. I thought of that last night and it kept me up.