It's just drawings, texts, added effects and sliding images. You can do it in Flash? or After Effects? There's probably a freeware that allows you to move jpgs around and add texts.

There's nothing special about how they're engineered.

What about this video ? Is it with the same effects ?

https://www.youtube.com/watch?v=k0HGg9J7sv0

I'd imagine it was After Effects, or something like it.

That being said, you could certainly get the same product using After Effects. Though they would create each element (backgrounds, characters, etc) in a separate program. There are quite a few good programs out there that provide an easy digital platform for art. I worked on a film recently that required some animation, and a friend of mine showed me the free program they use for their digital art:

http://firealpaca.com/en

In theory you could create your characters/backgrounds with that program, export them, and animate them in After Effects.

Hope at least some of this helps.

MS Paint.