Final answer:
The dum-dum cart has a special feature of a hidden compartment, which lends an additional element of play or utility.
Step-by-step explanation:
Aside from being a toy cart, the dum-dum cart has a hidden compartment. This unique feature allows it to store items out of sight, providing an additional element of play or utility. It doesn't play music, isn't made of gold, nor is it marketed as being customizable. The hidden compartment can be used for various play scenarios, such as secret deliveries or transporting items in a playful story context.