You could always work for Valve.

They literally troll their players with stuff like that.

When players misunderstood a joke, and assumed the Pyro was female, they ran with it. On the official class page about the Pyro, there's a script which will randomly replace "him/her".

When the Scout update was being shown, some players started a theory that it was really the Spy update, and on the last day of the reveal, the Spy would pop out. This didn't happen. Forward to the Sniper update, and halfway thru it, the Spy popped up on the announcement page, backstabbed the Sniper, and changed the name to "Spy Update". Update was released as a combo.

They constantly, CONSTANTLY hide stuff in other stuff. Unreleased weapons in videos, unreleased game modes get slight mentions. Every image that gets released with an update is scrutinized for clues. They like to play with the people who do this by putting out images that mean nothing. But usually, something that is revealed was actually hidden in a previous image or video.