Everyone probably already knows this, but I did find an interview with the devs of gen 5 and it's basically detailing the creation process of unova's pokemon, which gives some pretty good insight, especially if you wanna make your own fakemon legit.
For starter pokemon:
>What’s most important is that the designs don’t resemble any pre-existing Pokémon, and that the motifs fit the elemental types — which is what always takes the longest amount of time>These Pokémon are the first ones that young children — who have just become trainers and in a way are total amateurs — take with them to begin their adventures. That’s why these Pokémon shouldn’t look too strong from the very beginning — once they evolve, that’s when they start to look powerful. We always stick to this concept when designing starter Pokémon>We come up with all kinds of ideas, but if the motif isn’t well suited to a Water type, it’s easy for the the creature to end up looking strange. It can also happen with the Grass starter — for example, it’s weird if we end up with a Pokémon that’s just a dog with leaves growing out of it.>ut several lizard-based Pokémon already exist, so we thought maybe we should try a snake this time. However, we were afraid that a starter Pokémon that’s a snake from the very beginning might turn some people off, so Snivy got a set of cute hands and legs. And then Snivy becomes more like a snake gradually as it evolves, so it won’t seem so frightening (laughs)>We always divide the roles for the three starter Pokémon, by which I mean we assign each of them a distinct personality. For example, we make a cool one, a serious one, and a funny one.Source:
http://lavacutcontent.com/ken-sugimori-nintendo-dream-3/ 
