be a teddy bear

To be very kind and utterly harmless, especially in contrast to one's appearance or demeanor. I know he looks tough, what with his big muscles and scary tattoos, but trust me—he's a total teddy bear. Don't worry, the dog barks around strangers, but she's a teddy bear when she knows she's safe. She wouldn't hurt a fly. A: "You say your dad's a teddy bear, but he's never seemed that way to me." B: "That's because you're dating his daughter!"