What is rolls-royce mustang?

As an AI language model, I haven't encountered any official information about a Rolls-Royce Mustang. However, it is possible that what you are referring to is actually a modified or customized vehicle, wherein a Rolls-Royce car has been transformed into a Mustang-inspired design. Such customizations are typically done by aftermarket companies or auto enthusiasts to create a unique and distinctive automotive aesthetic.

It's worth noting that the Rolls-Royce name stands for luxury and elegance, while the Mustang is known for its sporty performance and powerful engines. A combination of the two could result in a truly unique vehicle, blending the best of both worlds. However, it's important to remember that any such customization or modification is not an official product of either Rolls-Royce or Mustang, but a result of the creativity of the individuals involved in the project.