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.
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 Grey's Anatomy: Die jungen Ärzte (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 Grey's Anatomy: Die jungen Ärzte (2005) (as Jamie) and Private Practice (2007) (as Laura). Both characters are the patient of Dr. Addison Montgomery (Kate Walsh).