Spark's Sprites

[Hoeloe]

By "off-balance", it is generally referring to the fact that he is leaning back. This is problematic, though, because it's very unnatural to lean backwards without having any kind of support.

When drawing characters (or anything, really), you should at the very least consider the centre of mass of the character. In most cases, this hangs around the middle of the waist, but if, for example, a character is carrying a large sword, it can change position depending on the weight distribution. Objects (including people) also have a base. This base is flat to the ground, and covers exactly the area between their feet (or connects together all the points that touch the ground). When you draw a line vertically down from the centre of mass, it should intersect with this base. If it doesn't, the character will fall over. On top of that, a more balanced pose will intersect the base closer to the centre, so even if your character is technically stable, it may look very unnatural.

Oddly enough, those 3 characters give perfect examples:



Your first character is unbalanced because his centre of mass intersects his base near the edge (note his centre of mass is further back than the other two because his head is drawing the weight). Your second character is balanced because the intersection is quite near the middle. Your third character, being that only one foot is actually touching the ground, will fall over, because her base is very small. Note that, even though she will fall over, she will fall onto her other foot, because she will fall towards her centre of mass.

Hopefully this helps a little.