Shannen Doherty isn't waltzing around the set of "Dancing with the Stars" for her health -- but as part of a deal she made with her father.

Shannen Doherty
Shannen told Ryan Seacrest today on KIIS-FM: "My dad on Christmas had a massive stroke and he lost his ability to speak and a lot of his mobility ... I mentioned DWTS as a joke because I'm so nervous in front of a live audience, he got really excited and we struck a deal."

The terms: She works on her fear of a live audience on the show and he'll work on his "speech and mobility."

"DWTS" premieres tonight.