"We're doomed, aren't we? Please, just say something, Princess!"

There are a number of different types of rubber suits, and they are all contagious for one purpose or another. Most are remnants of Alicorn civilization, once used to subdue lesser pony communities through pleasure or the simple dulling of their senses once the suit was applied. Another type was used to automatically protect the population of entire counties from plagues, spreading from wearer to wearer just as the disease it defended them against would. Whichever type is unleashed, those affected are rendered speechless, magicless, and capable of directly synthesizing the magic in the air around them in place of food and water.

I'll leave it up to you to decide which type Twilight is about to experience.