G
We
                B7
Are the Crystal Gems
                      C
We'll always save the day
                    Cm
And if you think we can't, we'll
              G
Always find a way.
                      B7            C
That's why the people of this world believe in
              Cm                     G
Garnet, Amethyst, and Pearl... AND STEVEN!



So, it's a pretty straightforward little song. Figured most of it out on my own 
pretty easily, then read Rebecca Sugar's Tumblr and learned that the Bmajor was actually a B7.

Not quite as easy as the Adventure Time theme, but pretty simple.