Cristián de la Fuente and Cheryl Burke's chemistry on the dance floor is undeniable. Primetime's sexiest partners are now bringing their combustible Cha Cha to the set of "Extra!" The heartthrob and the two-time "Dancing" champ reveal the hidden relationship they share on the set of "Dancing with the Stars."

"Dancer, old married couple, brother and sister relationship," says Burke. The two are comfortable with each other, and they're always joking around. Cheryl and Christian have twice danced with being eliminated -- and survived, but what happens when these budding friends step off the dance floor for good?

"The good thing is he lives ten doors down," says Cheryl, "so I'll just knock on his door!" Tune in to "Dancing with the Stars" next week to see this dynamic duo rock the Foxtrot!