The Efteling is rightfully called a theme park

Not only the rides are themed, but also the queues, food, walkways, street lamps, trash cans, ATM, maintenance signs, you name it. Every square foot of the developed areas is thought about into the tiniest detail.

And almost everything is made in-house. Every attraction starts with concept art by the park's own designers. Then their own technical department looks for existing techniques to make it work, or develops their own. All decoration is built in the on-site workshop. Their own construction crew is an expert in making new buildings look old. Every section gets its own music written by the house composer.

Aside from the occasional orchestra to record said music, pretty much the only outside help they hire is for ride systems. But even then the park approaches various builders with a list of requirements for a unique product instead of buying something from their catalogue, and stays very closely involved in the further design and build process from start to finish.

They are definitely not the easiest partner to work with, but manufacturers are usually honored to contribute to a product that meets Efteling standards.