Jackson and Callie in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Bailey in her wedding dress in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Bailey in her wedding dress in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Derek's sister Lizzie in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Dr. Derek Shepherd in his office in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Derek in his office in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Meredith and Derek in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Jesse Williams as Jackson Avery in another new photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Neve Campbell as Der's sister Lizzie in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Callie and Jackson in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Meredith and Derek look on in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.

Callie, Derek and Meredith strategize in a photo from "Run, Baby, Run," the December 13, 2012 episode of Grey's Anatomy.