Watch the episode of The Adventures of Mary-Kate and Ashley. The one where they go to the Navy. When they're there, and they're singing about the Navy, one of the twins has a wet spot on her shirt. The spot is only there for the first shot. For the rest of the song, they turned her shirt around, and you can tell because you can see the tag stitching. The last shot goes back to her wearing the shirt the right way, with a wet spot on it.