This reminds me of fracture Fairy tales with a bit of Dudly Do-Right thown in for good measure. Of course there are some more modern tropes sprinkled in, but it all blends well.
Honestly, this has better animation, writing, and definitely singing than several animations on TV. I'm not sure if this would make a good serial, but I wouldn't mind seeing more of Sir Knightley and his singing sword. If you do make more, please don't have him fawn over the same princess. That would be too predictable, and this animation had a few good twists.