I've only seen a few episodes of Wataru. It's one of my goals to see all of them eventually. I got these cels several years ago. I don't know which Wataru series each is from.
I vaguely remember her being a princess. She's very cute! I actually have four cels from this sequence - I got them a few years ago from Ninja Death Graphics.
I got this douga from a cel gallery that used to be in the mall near my parents house - I found it in a cheap folder for $5, so I went ahead and bought it. I have no idea what happened to the cel it was obviously once stuck to.