HOW TO MAKE NAME LONGER THAN 6 LETTERS!
You can also change name to "Undyne" or "ASGORE". It's quite simple, and NO I didn't steal this, I found it out myself.
1.) Press Windows + R
2.) Type in %appdata%
3.) Hit enter
4.) Look at the top of the folder, and click appdata.
5.) Go to "local" (Not locallow)
6.) Scroll down until you see "Undertale"
7.) Open the folder "Undertale"
8.) Double click file0 and open it with notepad
9.) Change the top line to whatever you want your name to be.
10.) Save file (And don't change other numbers in that file, those give you free items/levels/exp if you increase them, and drop your items/level/exp if you decrease them. (Example: The second line down is your LV, changing that to 99 will make your level 99, 50 will make your level 50, so on and so on.) Don't even try it you lil' cheater.
You're all done, just launch undertale. You can find an easter egg after you do it: Next to your name it will say "Easy to change, Huh?" http://steamoss.com/sharedfiles/filedetails/?id=737553701