Minnie soon became the very first add-on to the cast. Mickey wears them in nearly all of his subsequent appearances and several different characters followed suit. He played a major role in a big number of cartoons and books for children, such as the Imagination, Mickey Mouse Clubhouse, etc.. The cartoon wasn't the very first cartoon to feature a soundtrack joined to the action.
These days, many coloring books are used to market and promote children's movies or TV cartoon characters. Finding books containing basic illustrations of flowers, food, animals, etc are a bit more difficult, but not impossible. Themed coloring books are often best sellers.
Of course, finding and printing coloring pages from websites is also free. As opposed to spending $10 or more for a coloring book, you spend just cents per page as you print up what you need. Now, you might not think that it's a huge deal if you only did it once, but imagine if you never bought another coloring book again? Over the course of a few years you could literally save hundreds of dollars, and that's something that everyone can appreciate. You could even print up pages and make them into your own books, or give them as gifts.