Secret Levels
To unlock a secret level on the Level Selection screen, get an Expert Score on all levels in a Restaurant (ex Get Expert Score in all 10 levels of the Cruise Ship). After you unlock the first level, there will be a button on the Level Selection screen that you can click. There are 5 levels to unlock, one for each Restaurant.
Business Lunch - Get all Expert Score in the Submarine
Date Night - Get all Expert Score in the Cruise Ship
Everybody to the Limit - Get all Expert Score in the Rocket
Girls' Night Out - Get all Expert Score in the Rail Train
Summer Camp - Get all Expert Score in the Blimp