NBC said Knight will perform an "act of fire clowning" on Wednesday's edition of "Celebrity Circus."
Also slated to compete during the six-week series are model Rachel Hunter, actors Antonio Sabato Jr. and Stacey Dash, professional skateboarder Jason "Wee Man" Acuna, R&B singer Blu Cantrell and Olympic gold-medal swimmer Janet Evans.
The June 11 premiere episode of the show was watched by 6.5 million viewers overall and scored NBC's highest non-sports rating on any night of the week for the month of June to date in the adults 18-49 category, the network said.
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