Although Thiessen's publicist denies she will appear on the show, TMZ said its sources are adamant she will be there when the new season starts next month.
Thiessen's former "Beverly Hills, 90210" co-stars Shannen Doherty, Jennie Garth and Ian Ziering have competed on "Dancing" in previous seasons.
Professional football player Hines Ward won last season's mirror ball trophy.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Aaron Carter is still in love with Hilary Duff