I think you need some contrast for your main character. It's already blending with the BG, that he looks so much smaller than Johnny.
Black is a pain to work with. Also I would drop that black line between his hand and the shirt. You have a clear black line from the jacket arm, then a bit of the white shirt and then skin. Also I don't know the show, but how is the character normally? He's he conservative and keeps his jacket buttoned up for most of the episode, or is he more relaxed, like in the last picture you posted, and uses his jacket lose and open for most of the episode? Cause if it is the later, then I would go for an unbuttoned jacket, that would give you a little more contrast to an otherwise very dark character.
Here's a quick paint-over, just to illustrate. (remember that black is not always just black, but different kinds of grays depending on the lighting it's receiving.)
[IMGzoom]http://i725.photobucket.com/albums/ww258/Cassiebsg/Private/SpritesAlpha_paintover.png[/IMGzoom]
Also, think you are using way to many shades or color. Reduce them.
And do post the sprites in it's original size. painting over something that is 5 times the size it should be is a pain.
And last but not least, I'm not the best sprite artist, so listen to the "experts" (I'm not one).
Think Johnny looks okay, though again, I would avoid the pure white for the hair, try a very light of gray, leave the white for highlights and a light grey for shadows.
Black is a pain to work with. Also I would drop that black line between his hand and the shirt. You have a clear black line from the jacket arm, then a bit of the white shirt and then skin. Also I don't know the show, but how is the character normally? He's he conservative and keeps his jacket buttoned up for most of the episode, or is he more relaxed, like in the last picture you posted, and uses his jacket lose and open for most of the episode? Cause if it is the later, then I would go for an unbuttoned jacket, that would give you a little more contrast to an otherwise very dark character.
Here's a quick paint-over, just to illustrate. (remember that black is not always just black, but different kinds of grays depending on the lighting it's receiving.)
[IMGzoom]http://i725.photobucket.com/albums/ww258/Cassiebsg/Private/SpritesAlpha_paintover.png[/IMGzoom]
Also, think you are using way to many shades or color. Reduce them.

And do post the sprites in it's original size. painting over something that is 5 times the size it should be is a pain.
And last but not least, I'm not the best sprite artist, so listen to the "experts" (I'm not one).

Think Johnny looks okay, though again, I would avoid the pure white for the hair, try a very light of gray, leave the white for highlights and a light grey for shadows.