they aren't the same style. Not even close. ^^
The first two are simple pixel stuff. But not like actual pixels. Something that can be drawn up with a pencil in photoshop or even MS paint. It takes practice do to them cause its revolves around drawing on the computer with a mouse (or if your lucky, a tablet)
The third picture is a simple water color look style. Easily done by toning down on hard colors and creating soft colors, and also be done by downing the opacity. Can be done in multiple programs. Photoshop, Manga Studio, ect.
The thrust chibi is simply an animated pixel. You start with a base and move on from there. This one was started by:
http://i37.tinypic.com/2q3qema.gif the little thrust dragon. It was soon moved into a base and transformed into a human or w/e, clothed, and yeah. Takes practice to get the clothes just right and to change each layer so it has all the clothes and pixels. This animation has a good 4 Frames to make the animation
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I hope this helped somehow. >> <<
Just practice. Take some tutorials and your good to go. :D