There's more to it. At Google I/O a protestor interrupted a presentation to yell that Google made killer robots. There have been a lot of jokes internally about it. This is probably playing on that as well.
Re:Google.com/killer-robots.txt
by sschueller on Friday July 04, 2014 @11:03AM
(#7989014)
February 1994[1], so the 20 year anniversary of the robots.txt file.
Its the 20 year anniversary of the robots.txt file.
The new Google Easter Egg robots.txt was uploaded recently, on the anniversary of the Robots.txt file.
You can access the new Robots file at google.com/killer-robots.txt.
The new File Reads as:
User-Agent: T-1000
User-Agent: T-800
Disallow: /+LarryPage
Disallow: /+SergeyBrin
T-1000 and T-800 are the different versions of Terminators for the movie series, The Terminator. Here its telling these two killer robots to not kill the Google founders, Larry Page and Sergey Brin. Pun Intended.
Now Larry & Sergey are safe enough.