User blog comment:SporeVideos3/Why I think Club Penguin stopped making Animated Shorts/@comment-4835804-20140712190047

The title of Protobot Returns has "A Club Penguin Short" in it, so it can be categorized under the shorts. Also, all of the music video are considered "shorts", as they have animation style similar to the others.

And, it really doesn't matter how long a season takes. Club Penguin just has too much on their plate to make shorts ALL the time.