Chicago Fire star Taylor Kinney may be engaged to Lady Gaga, but Peggy Bundy will always hold a special place in his heart.

Yep, that's right. Kinney tells that the Married... with Children matriarch, played by Sons of Anarchy's Katey Sagal, was his first celebrity crush. "I never understood why Al didn't want to sleep with her," he admits. "Because I always did."

Check out the video above to see what secrets Kinney's Chicago Fire castmates reveal, including the most embarrassing songs in Jesse Spencer's and Monica Raymund's music collections. (Spoiler: Spencer is a closeted Madonna fan.)

Chicago Fire airs Tuesdays at 10/9c on NBC.