Why does Google's 404 page have such an odd title tag?

Question

I was looking at Google's 404 page, e.g.

http://google.com/asdf

It has the following title tag:

<title>Error 404 (Not Found)!!1</title>

The double exclamation marks followed by a 1 seems so... unprofessional. As if a programmer wanted to type three exclamation marks, but let go of the SHIFT key too early, and that was it. I mean, I have definitely done this kind of thing in a quick e-mail to remind my partner to PLEASE BUY ME CHOCOLATE!!1

But this just seems bizarre for a website like Google's.

Is there anything else to this title tag??