Idina Menzel played a brief love interest of Tim Daly's character (Pete) in Season 2 when in reality, she was married to Taye Diggs (Sam). There's even a scene of Sam approving of Pete dating Idina's character.
The girl painting in Violet's living room is the same painting in the doorway of the Gilmore Girls: Tal Mãe, Tal Filha (2000) home.
In the pilot episodes The Other Side of This Life, Part 1 (2007) and The Other Side of This Life, Part 2 (2007), which were part of season 3 of A Anatomia de Grey (2005), the role of Naomi Bennett was not played by Audra McDonald, but by Merrin Dungey.
The character Sam Bennett's nickname/pen name Dr. Feelgood is most likely a reference to the album 'Private Practice' by the band Dr. Feelgood released in 1978.
Alexandra Holden plays 2 different characters on A Anatomia de Grey (2005) (as Jamie) and Private Practice (2007) (as Laura). Both characters are the patient of Dr. Addison Montgomery (Kate Walsh).