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.
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 (2000) home.
The role of Naomi Bennett was played by Merrin Dungey in the pilot episode's Grey's Anatomy: The Other Side of This Life, Part 1 (2007) and Grey's Anatomy: The Other Side of This Life, Part 2 (2007).
Alexandra Holden plays 2 different characters on Grey's Anatomy (2005) (as Jamie) and Private Practice (2007) (as Laura). Both characters are the patient of Dr. Addison Montgomery (Kate Walsh).
Amanda Foreman plays 2 different characters on "Private Practice" (as Katie Kent, Violet's patient, who attacked her (the end of season 2)), and on Grey's Anatomy (2005) (as Nora, wife of a guy with no arms (season 7)).