Well, I decided to try it? I'm a huge fan of Gravity Falls and I have been replaying this theme song in my head that I need to do this! 
Instrumental made by the wonderful MusicByOctavia
Fanmade lyrics: missbunniswan
Vocals: Kathy-chan 
Hope you guys enjoy this short intro!

Gravity Falls Theme Song w/lyrics (Kathy-chan ver.)

Just a typical girl making some music and using my voice to bring awesomeness! 
I'm trilingual (I speak English, Spanish, and understand Japanese), so feel free to message me! 8D