It all started quietly. Several weeks ago Bruce Willis called to ask out Brooke Burns, the host of NBC's Dog Eat Dog. "They've had fun movie dates with kids and popcorn at each other's houses," a pal says of Burns, 25, who was divorced from Nip/Tuck's Julian McMahon last year. (She's mom to Madison, 3.) The ambience was decidedly more adult when Willis, 48, visited Burns last week in Costa Rica, where Burns is shooting the movie Death to the Supermodels. The duo hit the beach and breakfasted at a café. Says a witness: "They looked happy." And for the record, she's younger than Willis's ex-wife Demi Moore's boyfriend Ashton Kutcher—by a month.