Colbert Has 3 Theories About That Surprise Twist In Justin Bieber's New Video

"The Late Show" host analyzed the teaser for the Bieb's "Ghost" video.

Stephen Colbert was as surprised as anyone by the unexpected co-star of Justin Bieber’s newest video: Diane Keaton, who appears in a brief teaser for “Ghost.”

As Colbert noted, the appearance by the screen icon in the video left Bieber’s fans “confused.”

But “The Late Show” host had some theories.

“Based on that clip, she either plays Bieber’s love interest, his mom, or Diane Keaton, who just wandered onto the set of a Justin Bieber video,” Colbert cracked. “Hard to tell.”

It didn’t take long to get some answers, and none of Colbert’s guesses rated.

Bieber’s full video dropped late Thursday, and is about grieving the loss of a grandparent: