The Kat first appeared on World Wrestling Federation (WWF)'s flagship program, Raw is War, in August 1999. She debuted as Miss Kitty, an assistant to Debra, appointed to her by Jeff Jarrett, whom Debra managed. The partnership ended when Jarrett left the company after losing the Intercontinental Championship to Chyna at No Mercy. Because Jarrett was departing the company after the match, Kitty began managing Chyna, and then started dressing in 'Chyna-like' clothing and wearing a black wig.
At Armageddon in December 1999, Miss Kitty won her only WWF Women's Championship in a four corners evening gown pool match, by defeating then-champion Ivory, Jacqueline, and Barbara Bush by stripping them of their gowns. The special guest referees were The Fabulous Moolah and Mae Young. After the match, Miss Kitty stripped out of her dress in celebration and quickly flashed the crowd her breasts. The following evening, she announced before successfully defending her title in a chocolate pudding match that she was changing her name to The Kat. The Kat then appeared at the Royal Rumble in the 'Miss Royal Rumble Swimsuit Contest', where she appeared in a bikini made out of bubble wrap. The contest, however, was won by Mae Young. She lost the championship on the January 31 edition of Raw to Hervina in a Lumberjill Snowbunny match, a match that took place in a snow filled pool surrounded by female wrestlers whose purpose was to keep The Kat and Hervina from leaving the pool.
The Kat then began an on-screen rivalry with Terri Runnels. At WrestleMania 2000, Runnels (accompanied by The Fabulous Moolah) defeated The Kat (with Mae Young) in a catfight. Val Venis was the special guest referee, but he was distracted during the match when Young kissed him, which allowed Moolah to pull The Kat out of the ring. When Venis saw her out of the ring, he declared Runnels the winner. Post-match, The Kat attacked Runnels by stripping off her pants to expose her thong. The feud continued, and the duo had an arm wrestling match at Insurrextion. The Kat was victorious, but after the match, Runnels pulled The Kat's top off, exposing her breasts. The two women continued to feud throughout the summer, often in mixed tag matches. In June 2000, The Kat attempted to regain the Women's Championship by entering a battle royal to become the number one contender, but she was eliminated by her rival Terri. The feud resurfaced in a 'Thong Stink Face' match at SummerSlam, which The Kat won by performing a stinkface on Runnels.
In early 2001, The Kat began a new storyline with a stable called the Right to Censor, a group of wrestlers purportedly wanting to rein in the vulgarity of the "Attitude Era," during which she demanded equal time for the "right for nudity". At No Way Out, Jerry Lawler, who was representing The Kat, lost a match to Steven Richards, the head of the stable, after The Kat mistakenly hit Lawler with the Women's Championship belt. As a result of Lawler losing the match, she was forced to join the stable. On February 27, 2001, however, The Kat was released from the WWF in the middle of the storyline.