Cut the pound cake in half crosswise then cut each half lengthwise to form 4 boxcar shapes. Place the cake pieces on a platter to form a train. Divide the frosting into 4 bowls and add a different food color to each to create 4 different colors.
Frost each boxcar with a different color frosting. Use mini sandwich cookies to make wheels, Starburst candies for windows,Tootsie Rolls for a smokestack and licorice to connect the wheels and boxcars to each other. Serve immediately,or cover loosely until ready to serve.