They do but Its from a long list from which they choice from and they think it fits, It depends on the Gimmick. They will give you a list between 10 - 25 Songs and you picks out of those. It may not be the one you want but You will like one of those picks.
Written in the Stars- Tinie Tempah
yes she do sing the theme song
who sing my world the theme song of Jeff jarrett
They usually sing their own theme song.
Yes Selena Gomez does sing the Shake it Up Theme Song!
If its the theme song, it was Leona Lewis
No
Koji Kondo created the Super Mario Bros. theme song.
Yes, Laura Bailey does sing the English ending theme of Fruits Basket.
She sung the theme song to You only live twice
Hank Williams Jr. continues to sing the theme song for Monday Night Football for the 2008-2009 football season.
Alter Bridge are the band who sing Edge's theme song.