Some bot/crawler fun on Stack Overflow. 10 hours of fun, to be precise.

BotLovin.cs

private static readonly string[] tenHoursOfFun =
{
    "https://www.youtube.com/watch?v=wbby9coDRCk",
    "https://www.youtube.com/watch?v=nb2evY0kmpQ",
    "https://www.youtube.com/watch?v=eh7lp9umG2I",
    "https://www.youtube.com/watch?v=z9Uz1icjwrM",
    "https://www.youtube.com/watch?v=Sagg08DrO5U",
    "https://www.youtube.com/watch?v=5XmjJvJTyx0",
    "https://www.youtube.com/watch?v=IkdmOVejUlI",
    "https://www.youtube.com/watch?v=jScuYd3_xdQ",
    "https://www.youtube.com/watch?v=S5PvBzDlZGs",
    "https://www.youtube.com/watch?v=9UZbGgXvCCA",
    "https://www.youtube.com/watch?v=O-dNDXUt1fg",
    "https://www.youtube.com/watch?v=MJ5JEhDy8nE",
    "https://www.youtube.com/watch?v=VnnWp_akOrE",
    "https://www.youtube.com/watch?v=jwGfwbsF4c4",
    "https://www.youtube.com/watch?v=8ZcmTl_1ER8",
    "https://www.youtube.com/watch?v=gLmcGkvJ-e0",
    "https://www.youtube.com/watch?v=hGlyFc79BUE",
    "https://www.youtube.com/watch?v=xA8-6X8aR3o",
    "https://www.youtube.com/watch?v=7R1nRxcICeE",
    "https://www.youtube.com/watch?v=sCNrK-n68CM"
};

[StackRoute("admin.php")]
[StackRoute("admin/login.php")]
[StackRoute("administrator/index.php")]
[StackRoute("ajaxproxy/proxy.php")]
[StackRoute("bitrix/admin/index.php")]
[StackRoute("index.php")]
[StackRoute("magmi/web/magmi.php")]
[StackRoute("wp-admin/admin-ajax.php")]
[StackRoute("wp-admin/includes/themes.php")]
[StackRoute("wp-admin/options-link.php")]
[StackRoute("wp-admin/post-new.php")]
[StackRoute("wp-login.php")]
[StackRoute("xmlrpc.php")]
public ActionResult No() => Redirect(tenHoursOfFun[Current.Random.Next(0, tenHoursOfFun.Length)]);

Needs more http://heyyeyaaeyaaaeyaeyaa.com/

Edit 3 years later:
rip that site. At least https://www.youtube.com/watch?v=eh7lp9umG2I is in the list.

They're taking the hobbits to Isengard.

No "no undocumented administrative API for you" scheme involving YouTube videos is complete without a rickroll. Could you add https://www.youtube.com/watch?v=dQw4w9WgXcQ to the list of video URLs?

Suggested improvement: add [HttpGet] and [HttpHead] so that crawlers get trololled for HTTP HEAD requests too.

Some of videos are unavailable. For example, these: https://www.youtube.com/watch?v=ER97mPHhgtM,
https://www.youtube.com/watch?v=Sagg08DrO5U.

@GinoPane: first link is unavailable for me, but second link is available with no interruption until 6:12:24 (please double check)

What are the legal implications of this? Do we need permission from YouTube/Google?

What are the legal implications of this? Do we need permission from YouTube/Google?

I don't think there's any implication of this and that we need permission from YouTube/Google, this just redirects the client's url to a YouTube video.