I always find it amusing when I get a YouTube ad for something completely irrelevant to my life, like an ad for a one-time event in a different city, for over 65's, for a product category I've never exhibited an interest in. Like, I just imagine the marketing dude for that company looking at his incredibly low CTR in disbelief.

They left the targeting checkboxes all unchecked. Basically an intern wrote a free check to Google.