DOMINIC MONAGHAN
Onscreen: surrogate dad Former heroin addict Charlie helps Claire (Emilie de Ravin) care for her newborn, Aaron.
Offscreen: snuggly dude Former hobbit Monaghan, 28, has been spotted canoodling with costar Lilly, his flame of about a year. A source tells PEOPLE, "He hasn't felt this way about anyone else before."
Fun fact: How does Monaghan get in character? "I think I've only changed (clothes), like, three times on the island," he's said. "We're stinky."