I discovered an awesome YouTube Channel that I wanted to share. The channel is nmckaig. nmckaig recreates theme songs to movies and television shows using only his voice (all instruments are mimicked using his voice). Below are some of my favorites; be sure to check out his channel to watch more.
Bill Nye the Science Guy Theme Song
Star Wars Main Title Theme
The Simpsons Theme Song
Nickelodeon's "Doug" Theme Song