is there a word specifically for when you go buy one thing, but you come home with another, completely unrelated, thing instead?
like: "I went to buy bread, but I bought a sofa instead."
"I was supposed to borrow a wrench, but we started talking, one thing led to another, anyway here's complete works of Tolstoy, and a puppy"
"Blackberries? Oh, right, I *was* picking blackberries, wasn't I. 'Fraid might've left my basket in the woods. Anyway, meet my fairy fiancee."