Oh, welcome to AAH. I don't think I've seen you around before. It's always nice to see yet another fellow artist join the fun. I'm Mind-The-Gap, AKA Gappy. I'm here as an artist, first and foremost, but I'm also the AAH's forum mod. So if any issues regarding this forum crops up, you can come talk to me ^^
Your art is nicely done. It has potential for great things. Cute too, which is something I look for in art XD
Just a few suggestions for improvement - you may want to work on the head proportions. Some of them were drawn a little too wide. Perhaps you can start with a basic head shape first, with a circle followed by the cheeks. That aside, you've got a good knack for the body, arms, hands and clothing. All in all, you're on your way ^^ Keep it up!
We all copy other people's art to start off and practice. Even I did that to begin...though that was way back when XD However, we should always be honest with that and acknowledge the fact that they were copied. Never should we claim that it is our own work 100%.
By law, plagiarism IS illegal and is a punishable offense. This is especially true in commercial works. And no matter how much we say otherwise, it's what other people think that counts in this matter, unfortunately.
Take the case of the recent Bleach plagiarism, for example. So yes, it IS illegal. Never ever take or copy someone else's work without acknowledging it.
Anyhow, sorry for bringing this up XD Consider it friendly advice ^^