If you're only animating the mouth or doing very little body/limb animation, you can do it free with your windows Paint application. Draw your superhero, then make 5-10 copies with various mouth poses. Compose your audio then import your Paint images into Vegas. You can use the audio track as a reference point for your lip syncing. Of course, iIf you have Photoshop, Illustrator, etc. you can make more detailed characters and you can save the images as PNG files. You can then import them into Vegas as a sequence. I just recently got into doing this and it is a blast. Moho and other applications will save you a ton of time but if it's really simple animation, the above approach will work great.

(Edit...I forgot some important details...)
For some really cool fun, save your images with a pure blue or green background (make sure your superhero isn't wearing colors that match the background) then use the chromakeyer in Vegas to place your superhero in a video scene or various animated backgrounds.
This info is probably really old news to most of the guys here but I am like a kid when it comes to this stuff and it really is a blast!