Only last week I was talking to a colleague about the Tipp-ex video from a couple of years ago which allowed the viewer to rewrite an encounter between a hunter and a bear. It was a very clever and engaging use of video annotations and now Tipp-ex brought the idea to the next level in terms of creativity.
The 2012 version goes a step further and allows you to rewrite history. Users can choose which year they want to send the time travelling duo to, with some really great results. The Pac-man style game from 1980 is particularly fun.