The "Fifty Shades" star made the late-night host blush on Tuesday during her interview when they started talking about her mom, actress Melanie Griffith.
"My mom told me to tell you that she really loves you," Johnson told Letterman.
"Your mom used to come on the show all the time," Letterman replied. "And I really loved your mom."
Here's where things took a turn. "She brought you handcuffs one time," Johnson said. "So...are you my dad?"
Letterman laughed, raised his eyebrows at the audience and smiled. The pair then reminded everyone that Johnson knows exactly who her dad is -- "Miami Vice" star Don Johnson.
Johnson and Letterman also talked about her audition process for "Fifty Shades of Grey." Watch both parts of their conversation below: