Okay, have you ever played that game “Which of these does not belong”? In that game you are presented with a set of words or images and you have to identify the common link between them which will lead you to the odd one out – the one that does not belong.
This is not a mistake that professional game/movie/comic/character designers typically make – but it is one that beginners do frequently.
Sometimes it works to have one character that is strikingly different from all of the rest of the characters in a set. Sometimes it absolutely fails. To further confuse the issue, there is, as with most art related subjects, an element of subjectivity to this.
What concerns are there? If one character has different proportions from another it can suggest that the character is a different age (A bigger head suggests a child, for example). So, unless you intend to suggest a character is a different age/species by altering their proportions, then it is best to follow the rules you have created for your set so that people are not confused.
Having characters that look like they were all drawn by different artists is also typically a no-no. If you have one character drawn with thick black lines and finished with cell shading next to a character with thin colored lines and soft shading it might look like you ran out of money on your project and had to hire a different artist. It also doesn’t work well from a design prospective. It messes up the balance/chi/juju/continuity/whole-ness/feng shuei of your project – however you want to phrase it. Just throws things off. It would severely annoy someone with OCD and it doesn’t look particularly professional. If you don’t care, or have a good reason to do it, then it might work but this is rare.
Finding professional examples of this is nearly impossible. If you find one, feel free to submit it to me. I can only think of one right off: Kai Leng from Mass Effect 3 (awesome RPG from BioWare)
The whole game looks and feels like a modern star wars – and the worlds/characters are almost as well developed as those in the SW universe. Then, out of nowhere, comes this super flat (writing wise, though he is pretty thin, too) assassin who looks and acts like some 10 year old boy’s anime-ninja alter-ego. It’s almost embarrassing how badly written he is (mostly because he is quite stereotypical, cheesy, overdone). The rest of the characters look so unique and developed (even some that don’t get a lot of screen time manage to feel round in spite of it). Kai is very hard to take seriously and I hated every interaction with him. I couldn’t wait for my chance to kill that little design failure.
Mismatch that works:
If you have many artists working on your project and you can’t find a style they all can match, here are some things you can do about it:
1. Have one artist do all the sketches, one do all the inking, one do all the coloring, and one do all the shading – or some variation of this so that everything still meshes.
2. Have one artist do all of the work for certain sets (like one artist does the first level world/creatures/items and a second artist does all of the work for level 2 so that everything is congruous within those levels).
3. Don’t make anything match. I have below an example of this tactic and how it works:
This site has a neat ‘scrapbook’ feel and contains art done by probably over 100 different artists with totally different styles. I know because I am one of them! The game is designed to appeal to creative types and has something for everybody (whether you like simple and cute, absolutely ridiculous, hideously ugly or majorly mechanical). The worlds and items are completely unique from one another, too, not just the creature and character designs. It works because everything is so different. It’s not just a few out of place pieces of art.