Jessica Simpson's sister, Ashlee, is eyeing a guest-star gig on NBC's American Dreams this fall. "She's a good friend of mine," series star Brittany Snow tells TV Guide Online. "I don't know who she'll play yet. It's up to her. I think she'd make a great Janis Joplin because she's got that raspy voice." Snow adds that Usher and Kelly Clarkson are in talks to reprise their respective roles as Marvin Gaye and Brenda Lee. And speaking of American Idols, Fantasia Barrino is also considering filling Aretha Franklin's heels. For more Dreams dish, read today's Party Boy column on NBC's all-star bash at the TCA press tour in L.A.