Here is a 'The Magic Tree House' theory I've been thinking about a lot lately. So if you haven't read 'The Magic Tree House' basically Jack and Annie can go to anywhere they want just by pointing at a picture in a book and saying "I wish we could go there" they will go to the place they pointed at. It is not confirmed by the author, Mary Pope Osborne, that they can bring in their own books since Morgan always has a book ready for them. But what if they could bring their own books? All they would have to do is bring in a manga, point at a panel anywhere in the anime, say "I wish we could go there" and !! they are in an anime.