Nick Lachey has some tough work on his hands: romancing the gorgeous Alyssa Milano on "Charmed." What's so hard about that? He's got to give it up: only "Extra" was on the set as the singer-turned-actor kissed his guest-starring role goodbye.

For six episodes, Nick has "charmed" Alyssa's character as the ghostwriter who takes over Phoebe's advice column. "It's fun to have those flirty moments and to have those underlying romantic tensions there," Nick told us.

And what about his real-life romantic tension? As newlyweds in real life and on MTV, Nick said his superstar wife Jessica Simpson doesn't get too jealous about his romantic moments. "She's had romance on screen herself," he explained. "So she certainly understands the difference between personal and professional."

And speaking professionally, Nick revealed that rehearsing scenes and running lines is easier than reality TV. "The reality show is all day, every day," he said. "You feel like you're always on… Well, you really are always on."

You can catch Nick's last lip-locked with Alyssa on the WB's "Charmed" Sunday night.