Yeah that happens to me a fair bit.

The other one I found myself in, is that something they say reminds me of A, and I think it would be funny if B, so I jump to conclusion C, and then try to make a joke about D, completely skipping past and not even mentioning everything that transpired in my head that lead to E.

Big time daydreamer and conversation pre-planner over here. So, yes.

Maybe not so much that I remember saying things that I didn't, but more like:

I need to tell them X, Y, and Z.

"Y!" 🤦🏻‍♂️

My wife does this all the time. Multitasking on her phone, talking to multiple people at once, she'll often say something to me with zero context. She had the first part of the conversation in her head. Sometimes she will swear she told me something that she definitely hasn't as well.

Yes but luckily not too frequently

I go through a ton of hypothetical conversations like that in my head. So far I was always able to discern between real and made up though as far as I can tell.

I can't "imagine" conversations in that way, so it's not something I've experienced

No, but I'm hardly sane

Not often, but sometimes I can't remember if a conversation I had really happened in person, online, was entirely in my head, or just part of a dream I had.

I often have dreams about having conversations with peoole I know, often abiut really mundane stuff. It's very annoying, because my memory isn't great i genuinely struggle at times to figure out if it happened for real or was just a dream. Often I realise because it was impossible, like I'll be telling my parter that I chatted to X about something and they'll ask "when did you see X?" and I'll realise that I haven't seen them in weeks so I can't have had that conversation. It's even come up at work and I've had to check with coworkers, "have we spoken about this already?" (although I try and keep the "or did I just dream it" to my self).