In October 2013, The Washington Post reported on an analysis of documents obtained from Edward Snowden in which details about the NSA's interception of Google and Yahoo data transmissions were revealed. Among the information were a couple slides that were revealed, one in particular that was said to have riled Google workers.
One slide in particular featured a hand-drawn diagram showing a possible means by which it could intercept data from Google's servers. On this diagram -- featured below -- is a section reading "SSL Added and removed here!" with a little smiley face next to it. When shown to Google workers by The Washington Post, they reportedly "exploded in profanity" and encouraged the slide to be published.
Google recently released the source code for an upcoming Chrome extension called End-to-End that gives users an option for encrypting messages. In this code, it was discovered, Google took a bit of a jab at the NSA, adding in an Easter Egg referencing the above slide.
The code snippet, spotted by Twitter user Zen Albatross, reads "--ssl-added-and-removed-here-;-)". The message, though merely mirroring the NSA's own words, is rather poignant.