time for the park's annual Halloween event, Halloscream. In 1996, the upcharge attraction, Top Eliminator Dragsters opened. The park made its most expensive investment yet with the addition of Chang in 1997, a $12 million stand up Bolliger & Mabillard coaster that set the world records for stand up coasters in height, drop, length, speed, and number of inversions. The coaster also included a vertical loop that was tall, which was the tallest in the world. Thrill Karts (also known as Kingdom Go Carts) were also added this year, but were an upcharge attraction. Through the 1990–1998 seasons the park was considered as the fastest growing amusement park in North America. Park attendance had increased from 130,000 guests during the 1990 season, to 1.2 million guests during the 1997 season. Six Flags era (1998–2010) Kentucky Kingdom announced on September 26, 1997, that the rights to operate the park would be sold to Premier Parks for $64 million; the deal was finalized on November 7. As part of the agreement, Premier Parks agreed to continue bringing new attractions to the park through at least 1999. At the time, Kentucky Kingdom was one of the main tourism attractions for Louisville, receiving more visitors than Churchill Downs. On April 1, 1998, Premier Parks purchased Six Flags from Time Warner, and as such, on June 21, 1998, Kentucky Kingdom became known as Six Flags Kentucky Kingdom. Also on June 21, 1998, Twisted Sisters, a wooden dueling roller coaster, officially opened to the public. The roller coaster cost $5 million, and had been planned by Thememparks LLC, who originally wanted to name it "Double Trouble." Hook's Lagoon, an interactive tree house with water activities, was also added that year to Hurricane Bay. Six Flags then transformed King Louie's Playground into Looney Tunes Movie Town and added the Batman Stunt Show Spectacular in 1999. It became the ninth amusement park to use the Six Flags name. The Penguin's Blizzard River opened in 1999, using many pumps and mechanisms for a rapids ride that Premier Parks who had previously purchased the parts from Opryland USA. The parts were from Grizzly River Rampage, a rapids ride, that closed along with Opryland in 1997. That same year, the Vampire roller coaster was removed due to several malfunctions that had occurred earlier in the season. The ride would later reopen as Flashback at Six Flags New England in 2000. The