Plotagon is a free iPad app and free software for Mac and Windows that you can use to tell stories.You do have to sign up to use the app. Here’s an intro video:
Take a look at some of the videos that have been made on the Discover page. The voices are robotic, but the app is very easy to use and you can create a short play in no time.
Once you’re ready to create a story, you have three characters and and one free scene (a classroom), and the possibility of purchasing more (in-app purchases). Then you create your story by selecting characters and where you want them to be, adding a script, emotions and movement. You can also add sound effects and music. Once you’re finished, click on “share” and you can upload it to the website, where you’ll get a public URL you can share. You also have the option of publishing it to your YouTube account.