The lovebug seems to have bitten Blake Lively and Penn Badgley -- the onscreen couple have taken their romance offscreen. "No one is really supposed to know that," an insider tells the New York Daily News. "I was told by a friend of the family." The couple was also spotted looking totally together earlier this month. (Stinks for Blake's former BF and Burbank High School classmate, actor/model Kelly Blatz!)

Aww -- wonder if Blake and Penn double date with co-stars Leighton Meester and Chace Crawford!