The David Tennant Treat 4 Today is just a random photo of David Tennant.
It was taken when he was in the pantomine (on the radio) with Christian O'Connell a few years ago.
David also, later that week, wore the costume to Matt Lucas's wedding. (It was a fancy-dress do rather than David just dressing up for the fun of it!)
As usual, click the photo for a larger version.