<Tr> <Td_colspan="2"> Grey's Anatomy & Private Practice character </Td> </Tr> <Tr> <Td_colspan="2"> Kate Walsh as Addison Montgomery in Private Practice . </Td> </Tr> <Tr> <Th> First appearance </Th> <Td> Grey's Anatomy: "Who's Zoomin' Who?" (1.09) May 22, 2005 (as guest star) "Something To Talk About" (2.07) November 6, 2005 (as series regular) Private Practice: "In Which We Meet Addison, a Nice Girl From Somewhere Else" (1.01) September 26, 2007 </Td> </Tr> <Tr> <Th> Last appearance </Th> <Td> Grey's Anatomy: "Didn't We Almost Have It All?" (3.25) May 17, 2007 (as series regular) "If / Then" (8.13) February 2, 2012 (as special guest) Private Practice: "In Which We Say Goodbye" (6.13) January 22, 2013 </Td> </Tr>

What happened to dr montgomery in season 4