Anyone who knows any serious artist, or even a talented non-serious artist, knows the general stance on tracing stuff that isn't yours: Don't do it.
But why? WHY IS TRACING SO WRONG? Why is drawing Totoro from memory infinitely better than eyeballing work someone else has done? The argument seems to be that people learning how to draw should be allowed to trace or otherwise copy someone else's work by eyeballing it. But if you don't encourage originality, you get people who never STOP copying other people's work. You get fantastic artists who ONLY DRAW what they can look at directly. You learn amazing technical skills from looking at something and copying it, but you don't put any life into your art. You kill your creativity and your talent.
To be fair, everything drawn is referenced from something. But there is a difference between going to Getty images to see how the form of a foot is created so you can draw it accurately, and copying the entire drawing, including the foot.
I am against tracing mainly for that reason. The argument that people trace/heavily reference in order to learn how to draw is bullshit. It's a crutch. If you want to encourage someone to learn how to draw, hand them a drawing pad and a pencil and take them to the zoo. I guarantee any drawing from life will be 3,000x more interesting that something copied from a photograph, even if the technical skill is less. Drawing in the moment, achieving motion and weight in your art, is a much more admirable endeavour that Getting It Perfect. Getting soul and feeling into your work is a much higher accomplishment than reproducing a photo you took yesterday.
Don't be afraid to make mistakes. If you're tracing/drawing someone else's work, you can blame your errors on the original drawing. But how do you learn, then? As I'm drawing something original, I'm constantly thinking to myself, "How can I improve this? Why does this look wrong to me? Holy crap! That looks amazing! I'll have to remember how I did that! Aw, I have to erase this part, it just doesn't look proper." etc. You aren't ever going to accomplish that if you aren't drawing something original.
So, there's that.
The other thing is.
You're TAKING someone else's ART and CLAIMING IT AS YOUR OWN.
How messed up in the head do you have to be to actually believe that that's okay!? How did you never learn that stealing is wrong?
And I don't give a shit if you """"""""CREDIT""""""""". Unless the original owner has given you permission, it's immoral. And not only is it immoral, it's fucking illegal, you morons.
For our next exhibit, let's take a look at International Copyright Law. The United States and maaaany other countries throughout the world (hint: You can't get around this by claiming you don't live in one of them. Chances are you do) are members of the Berne Convention, which set up the laws and punishments for breaking the laws of copyright.
Article 2 of the Berne Convention defines the works that are covered by it:
"The expression "literary and artistic works" shall include every production in the literary, scientific and artistic domain, whatever may be the mode or form of its expression, such as books, pamphlets and other writings; lectures, addresses, sermons and other works of the same nature; dramatic or dramatico-musical works; choreographic works and entertainments in dumb show; musical compositions with or without words; cinematographic works to which are assimilated works expressed by a process analogous to cinematography; works of drawing, painting, architecture, sculpture, engraving and lithography; photographic works to which are assimilated works expressed by a process analogous to photography; works of applied art; illustrations, maps, plans, sketches and three-dimensional works relative to geography, topography, architecture or science."
Essentially, everything you can do or think of to do.
Article 9 states that:
"Authors of literary and artistic works protected by this Convention shall have the exclusive right of authorizing the reproduction of these works, in any manner or form."
IE: You can't trace something and credit the author. You have to get their permission to copy their work.
Now for the bad news.
Your fan art and mine is borderline infringing on copyrights. I say 'borderline' because of the fact that there is some wiggle-room for fair use and parody, so long as you aren't taking an exact reproduction of something and pasting it onto something else and calling it art. (For case law on that, please see Jeff Koons.) However, we are reproducing intellectual property in ways that hedge on illegality, and for that, we are at the mercy of the companies whose work we emulate.
The GOOD news is that destroying a fandom is one of the worst things a company can possibly do, and so this borderline infringement is generally overlooked in favor of fans that continue to pay money toward a copyright, but don't make money off of it themselves. Essentially, banning fanart and fanfiction would be such PR suicide that it would completely kill the interest in any particular franchise... Which is why Disney's lawyers aren't suing everyone who draws Lion King fanart. Because fandom promotes interest in a product, some companies like Blizzard and South Park Studios actively encourage fanworks.
If you want an example of how rabid copyright holders have destroyed their own franchise, please take a look at the Pern series by Anne McCaffery, who did not allow art of her characters, roleplaying games related to Pern, or fanfiction until she finally relented and relaxed her rules in 2004. Her son actively tried to claim that all dragons were a trademark of the Pern series, and many fans were sued for the devotion and love of the stories. People lost their life savings over books about dragons. While that was fully within McCaffery's rights to do so, the fandom suffered until she realized she was shooting herself in the foot.
But this is where copyright law gets more complicated. Let's say you find an original fanart drawing of Toothless from How to Train your Dragon. You like it, so you trace it.
Did you know that even though the original work is derivative of a copyright, the new work is also copyrighted? If you trace someone's work, you are infringing, and if they choose to tell you to take it down, you cannot use the argument that it is already derivative, so it's your right to keep it up. They can take you to court over it. And while that would not be wise, as they couldn't collect any monetary damages from you, you would be out hundreds of dollars in court costs and legal fees, because the court would rule against you.
So don't do it. It's illegal.
(References: Berne Convention, revised text: [link]