Nickelodeon Universe is opening an indoor themepark this week in East Rutherford’s American Dream Mall. It is said to be the largest indoor theme park in the country with more than 35 rides and attractions. Some big stars will be able to greet the little kids, too, like SpongeBob, Dora the Explorer and the Teenage Mutant Ninja Turtles. DreamWorks Water Park is slated to open next month and will feature more than 40 water slides. It will be the largest indoor theme park in North America.