Okay so this is basically the result of Wash and South getting Eta and Iota in that one au.
The way it works is this: Eta and Iota are constantly projecting to one another, and so quite often will project their hosts thoughts as well, and these can then be transmitted to the other host. So: Wash can send something to Eta, who sends it to Iota, who sends it to South, all in the space of a few seconds. (If you’ve read any of the Pern books, think of it like how Dragonriders communicate using their dragons. If you haven’t read any of the Pern books, use your imagination.)
On missions, this is useful because it allows Wash and South (and thus their teams) to relay information to each other even if they’re on radio silence. It also makes Wash and South an incredible team because they’re so perfectly in sync with one another (with some practice).
Unfortunately, it takes awhile for Eta and Iota to get the hang of not transmitting stuff. It takes awhile for Wash and South to learn how to keep certain of their thoughts away from their ai. It takes awhile for Eta and Iota to learn how to filter the things they do get and transmit. And before all that happens, South and Wash are stuck with each other’s thoughts constantly being broadcast to each other. And South finds out that Wash has this massive crush on her. And that no matter how hard he tries, he can’t stop fantasizing about her.
And not all of his fantasies are sexual. Some of them are weirdly romantic and sweet. But it’s awkward because she’s never thought of Wash like that, only now she’s starting to, and she doesn’t want him to know because she doesn’t want to get his hopes up.
But she’s starting to enjoy his fantasies. She’s starting to look forward to them.
Also, Wash has a filthy, filthy mind. She wouldn’t have expected it from him, him being such a boy scout and all, but wow. Wow. You think about your mother with that mind, Wash?