What a thoughtless, jerky attitude. Two seconds of poking around Twitter would have found you many real examples of horrified GMail users dealing with the fallout from this "prank", not just people dealing with a job search and potential employers, but people writing very emotionally charged e-mails, like condolence notices to people on the death of their child.
Which now has a Minion GIF in it.
It is one thing for a prank to do something to the UI of a product, like invert the colors or display Comic Sans. It is quite another when it alters the content of the very messages you are passing.