Retail Syndrome
When you go out shopping to buy a couple of things but have an urge to buy even more. Generally followed by silly excuses, e.g. I needed one of those, we're running out of them, it was on offer. Women suffer most from it.
Dude 1: I went into fake-mart to buy a pack of smarties, and I walked out with a whole cow!
Dude 2: Dude 1, you've suffered retail syndrome!
Dude 2: Dude 1, you've suffered retail syndrome!