When you turn on the game, you will see splash-screen:
Also special music can be heard in background. Pressing any key will activate main menu of the game and will close the picture and the music will change.
Currently this is the only intro the game have, but the developement team leave a place for a short movie.
If you have any idea (and possibility) how to make the movie, you are very welcome to do this!
wl.widelands.org/forum/topic/1897/ (splash screen bug and conclusion to save the screen for a short movie)