When my mom tells me important information just AFTER the relevant point in time. For instance, she told me my entire family is allergic to sulfa antibiotics, and my uncle nearly died from taking them, right after I took the first dose. (FTR, I broke out in oozing hives head-to-toe the week before my PhD qualifying exams.)
Last night, as I was on the phone with her and talking about how incredibly tired I was and happy that I'd finally finished making all 10 different kinds of treats and was busy boxing them up to ship, she said, "Oh, by the way, did I tell you that your sister just went gluten-free?" ARRGGHH!
In fact, it's not as bad as it might be, as the box contains some flourless chocolate cookies and some sour gummies, as well as spiced nuts. But, she knew what I was making for the last 2 weeks! Couldn't she tell me before then?