An option in online polls that is nonsensical and no one is expected to choose that. (Of course, if the poll itself is pretty nonsensical, like many of these polls are, seeing which one is the most nonsensical can be hard. It's usually the last one.)
Slashdot uses this sort of polls often (the current poll seems to have "CowboyNeal" as the possible cause of the Armageddon, which I suspect isn't that nonsensical scenario afterall), and in Kuro5hin the poll option is often "Inoshiro". (There is a theory that states that every story with "Inoshiro" as a story poll option gets rejected... It sometimes is the case.)
This sort of poll options usually sneak in, no matter how "serious" the poll tries to be. (Comment from a random European: This is great! USA takes the polls, surveys and especially the elections way too seriously, anyway. Mmmmmaybe they shouldn't allow this sort of candidates in presidential elections, though. They have a point, there.*)
The term "obligatory nonsensical answer", then, was used by Suck when they parodied Slashdot.
* Sorry, it's late in the night and I got a weird idea. No offense intended to anyone.