Bookmobileguy humor

Becky: A group of lions is called a pride.
Bookmobileguy: yes.
Becky: A group of cows is called a herd.
Bookmobileguy: Okay
Becky: A group of dogs is called a pack.
Bookmobileguy: Your point?
Becky: So what is a group of bookmobiles called? A fleet?
Bookmobileguy: No. A group of bookmobiles is called "a band."
Becky: Why, on earth?
Bookmobileguy: Because, we "Shake, Rattle and Roll!"