Beat the specified mission in Historical Campaigns to unlock the art gallery.
Name a profile Jub Jub to make everyone Ewok size.
Go to "Historical Campaign" mode and select the era you want to play (Clone Wars or Galactic Civil War), then enter the following:
Play the level 'Echo Base' and get the Taun Taun (The donkey creature) that is standing in front of the hanger. Go into the hanger and turn right, you will see a wall with boxes beside it. Go to the space between the boxes and you can walk through the wall.