I'm on a cartoon roll now, trying to remember all my favorites. This, obviously was one. So you can sing along if you'd like....
"When criminals in this world appear,
And break the laws that they should fear,
And frighten all who see or hear,
The cry goes up both far and near for
Underdog! Underdog! Underdog! Underdog!
Speed of lightning! Roar of thunder!
Fighting all who rob or plunder!
Underdog! Underdog!"