Nice! I like that you're doing something unique. Though it is still "old character next to young character" it is different enough that you want to watch.

One thing to keep in mind is the weight. On the large character, he has almost all his weight on his back arms. BUT when he lifts his arms to put them behind his head, 100% of that weight hits his abs (or those muscles anyway!). It's very tough to hold that position unless you're in great shape, and I don't feel like the blobby-fellow is in great shape considering his, well, shape.

Just keep that in mind. Always consider gravity, especially when doing 2D.

I wrote an article about it a while back, and though it looks a little like I'm just plugging my own work, here's the link: http://www.animatorisland.com/?p=875 If it helps you, that's what it's THERE for. That's why I wrote it. And anyone who rolls their eyes that I keep sharing the stuff I wrote can keep rolling their eyes, I wrote it to share!

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Updated work in progress; still have to do a few more things to the animation

Thanks for the feedback.