「Why do the crew members sing when they receive a tip?」
The "Entertainment Factor" is meant to lend a fun, festive atmosphere in our stores and to set us apart from the competition. We seek out crew members who like to perform and we "audition", rather then "interview" them. Many of our crew members enjoy the singing so much that they develop new songs themselves.
"they develop new songs themselves"ってことなので、スタッフで作る歌もあるようです。日本のコールドストーンでもそうなのかしら。。。