I noticed today in the Low Quality Posts queue, there were at least 2 votes of "Looks OK" on this answer to the question about bug spray in airliners. It's deleted now, but this was the text of the answer:
The spray is part of a covert govt. operation to test zombie-apocalypse inducing viruses on unsuspecting patrons.
I know that a little more levity is usually allowed here than on some other SE sites and I personally like it that way, but that's pretty clearly not a useful answer to the question. I could understand it as a joke comment on the question, but it really doesn't seem like it belongs as an answer.