♪ ♪ ♪ everybody count down ♪ the new cast of "dancing with the stars" was introduced yesterday on "good morning america." >> the group includes actors, olympians and a brand new co-host. as brandi hitt tells us, there's also one big new plot twist this season. >> reporter: they are shimmying, twirling and strutting their way onto season 18 of "dancing with the stars." >> i thought i'd meet the challenge. >> i'm scared to death. >> reporter: the new celebrity cast including danica mckellar, "full house's" candace cameron bure. >> we are just going to rally. >> reporter: there are several top athletes.