Spark's Sprites v2.0

[Gors]

While you are correct, making sprites off a model sheet is indeed the proof that they are stiff (the poses in model sheets are stiff indeed)

But even if you edit the sprites, it's not just the leg height that changes, you can notice that some has thinner legs and some even have a different spacing between legs. The original poses show the character in a full frontal view but your sprite has 3/4 body and frontal legs which makes the problem even more blatant.

The feeling of cram comes from the exaggerated use of dark pixels in a small space. As you may know in pixelart, similar colors tend to 'merge' when seen in 1x, this includes the black line over the eye merging with the hair outline on their foreheads.

Anime styled sprites avoid that by using a lighter color for the hair outline, as seen here . I think you could benefit if you used a similar technique for it.