Subscribe to the all-new Rolling Stone! Everything you need to know from the authority on music, entertainment, politics and pop culture. On a nondescript, cactus-lined street in Sherman Oaks, California, it’s hard to miss the only house with a unicorn-drawn-carriage and a custom BMW painted like a rainbow race car on its curb. Inside the house, singer, actress, and YouTube superstar JoJo Siwa is covered in flour, sprinkles, and eggs, filming a scene for JoJo’s Dream Birthday, a one-hour special celebrating her 16th birthday. When it airs six weeks later in May on Nickelodeon, her network home of more than two years, it will be right after the first show of her 81-date headlining D.R.E.A.M. Tour and will rake in over 800,000 viewers across all platforms. Like Siwa herself, the house is colorful and chaotic. The main room looks like a museum’s special exhibit with her sequined outfits preserved within glass cases. Her kitchen features a wall of candy and a nacho machine. The bannisters are wrapped in rainbow garland leading up to a second floor accented with gummy bear balloons and a giant Siwa-shaped pillow. If you were one of the 17 million people who watched her YouTube vlog ...