How do you change your username?

YOu have to PM a moderator or admin (I actually don't know the difference so Sméagol is a good choice. He owns everything.)

I thought of Heinous Spaghetti once

I pretty sure only administrators have the power to change usernames (ie Smeagol). On the topic of names I'll probably try and get mine changed to match up with my new YouTube account sometime soon.

People would expect only the one type of film, and it isn't very good if you decide to expand out to other genres.
I suggest something more generic.

Nothing with studios. "Studios" isn't even accurate since it's really just you, and if I had thought about it a little more when I was starting out in 5th grade, I wouldn't have gone for it. I suggest something distinctive and memorable that doesn't have "productions" "studios" "labs" "films" etc. in it.

"Brick" is also a nice one to avoid simply because half this site uses it in their names.

-Sméagol Studios

True.

Personally, I like Heinous Spaghetti.

I second that suggestion.

When I was choosing my band name, I had a list of over 100 names.  I actually want to do a song about that process.  Anyway, to help choose a good name (I settled on Tinnitis), I imagined a DJ announcing a song, saying, "Now here's the lastest hit from [band name]!"  I guess the best way to transfer this is to imagine what the production card at the end of each of your films could look like with that name.  Hope this idea helps!