The It's Complicated star dashed onto the set of the Conan show when host Conan O'Brien refused to give back the headgear after trying it on.

O'Brien said, ""I love this hat,"" prompting a worried Blunt to state, ""You can't keep it... because it's John's hat... He's very fond of it.""

The host protested and the actress' husband stormed on from the wings, took the hat off O'Brien's head, waved sweetly at his bride and walked off.