Valve recently updated the ending to Portal. And by "updated" I mean changed. Altered. Retconned.
The original ending has Chell on the ground outside of the Aperture Science building, apparently escaped. The new ending adds just a few seconds of action, showing Chell being dragged away by an unseen robot. The change allows them to connect Portal to its upcoming sequel and sets the stage for Chell to once again be a prisoner of some loopy AI.
This is certainly an unprecedented move. Has anyone else ever altered the ending of their game in a patch after launch? I can't think of any examples.
Is it too late for someone to patch up the end of Knights of the Old Republic II? I'm just asking.