Really cute drawings Elecktronick! I do have a crit for the last piece tho, the girl's expression is very off, alot of people fall into this trap coz they're so used to drawing smiles like this and don't realise that the same principle doesn't apply to every angle. The shape of the mouth does actually change dramatically from our perception under extreme angles, in this case the undershot. The smile you drew on the girl could be thrown on a front-view portrait of any character, the angle of the teeth, the smile, everything.
I didn't want to bother trying to explain my crit, it's better if I just drew it out:
I drew my thoughts/reasoning on the upper right, the mouth still follows the same curve as the eye line guide-line thing (I'm not sure what that trick is called). What dictates the frown into a smile is the cheek muscles, if you're smiling the cheek potrudes outwards and you get this line crease that connects the side of the mouths to the nose. Don't be afraid to paint darker tones in young characters, they still have them!
Popular animes and art culture has taught us that drawing the smile-crease line makes characters appear OLD, but thats completely wrong! It only appears that way because its missing the other shadow elements that plays off the line. Here's another somewhat-related example:
Without the other compositional elements, the first pic looks like a hitler-stouche. The second reveals this to be merely a shadow. The same applies to drawing the shadows on the smile-line. Aaah I'm going off on a tangent again. But I hope you learn something from this.
All the best.