Grey's Anatomy and Private Practice Crossovers

Grey's Anatomy and Private Practice have had multiple crossovers events, allowing characters to appear in either series for a storyline. Since the debut of Private Practice during the fourth season of Grey's Anatomy, several crossover events between the two series have occurred. The characters of Addison Forbes Montgomery and later Amelia Shepherd are often at the forefront of the crossovers. 
As of yet, a total of nine crossover events have taken place. The most prolific crossover occurred in February 2009 and featured many characters from each series crossing over.
==Backdoor Pilot, May 2007==
*Episodes: The Other Side of This Life, Part 1 (GA) and The Other Side of This Life, Part 2 (GA)
*Characters Crossing Over: Addison Forbes Montgomery, Naomi Bennett, Sam Bennett, Cooper Freedman, Violet Turner, Pete Wilder, and Dell Parker
The Grey's Anatomy episodes "The Other Side of This Life, Part 1"  and "Part 2" served as a backdoor pilot for what would become Private Practice, introducing all characters that would later form the main cast of the new show (except for Charlotte King).
The plot revolves around Addison taking a sabbatical from Seattle, and going to LA to visit her old friends, Naomi and Sam. Naomi is a fertility specialist; one of the best, according to Addison, and would be the person to get Addison pregnant. Over the course of her visit, Addison ends up signing onto a medical case and performing surgery. With the departure of the practice's previous OB/GYN, Addison is offered a job at the practice as the new OB/GYN.
==Addison's Departure==
*Episodes: In Which We Meet Addison, a Nice Girl From Somewhere Else (PP)
*Character Crossing Over: Richard Webber
While Addison's departure from Grey's Anatomy is not shown or stated during the season finale of Grey's Anatomy, the first episode of Private Practice shows Addison and Richard Webber fighting over her decision, and Richard accepting her resignation.
==Addison's Return, May 2008==
*Episodes: Piece of My Heart (GA)
*Character Crossing Over: Addison Forbes Montgomery
Due to the Writer's Guild Strike of 2007/2008, Private Practice ceased production with the original order of nine episodes fulfilled and the remaining 13 ordered not produced. It was felt that Addison should return to Seattle Grace, and she did so in the Grey's Anatomy episode "Piece of My Heart" after the strike.
In the episode, Addison returns to Seattle Grace, insisting she is "not back" and is only there for a consultation. She realizes many things have changed since her departure, and, curiously, foreshadows events that will occur. Richard offers her her job back, but Addison declines. Although the "blood and stench" of surgery makes her feel good, she comes to realize that it was right for her to leave.
==The Grey's Anatomy & Private Practice Crossover Event, February 2009==
*Episodes: Beat Your Heart Out (GA), Acceptance (PP), Before and After (GA), Ex-Life (PP), and An Honest Mistake (GA)
*Characters Crossing Over: Addison Forbes Montgomery, Naomi Bennett, Sam Bennett, Alex Karev, Miranda Bailey, Richard Webber, Derek Shepherd, Mark Sloan, and Joe the Bartender.
After the success of Addison returning to Seattle for one episode, the idea of a large scale crossover between the two shows was created and was something both the creative forces behind the series and the network were keen to produce. The fourth crossover was marketed as the "Grey's Anatomy and Private Practice Crossover Event" by ABC. The event was much more significant affair compared to the previous crossover, which only included Addison. The February 2009 crossover consists of continuous storylines over both Grey's Anatomy and Private Practice and features stars from both series. There are two main story lines which cross over into each series, both involving Derek and Addison.
The first storyline involves Addison's brother, Archer, as he is diagnosed with neurocysticercosis (parasites in his brain) and he is rushed to Seattle Grace. Although Archer and Derek share a mutual distrust of each other, Derek is one of only a handful of neurosurgeons in the world that could perform his procedure successfully.
The second storyline involves one of Derek's pregnant patients, Jen Harmon, who has an aneurysm in her brain. Following a mistake in surgery, Addison diagnoses mother and baby with Mirror Syndrome (the mother is suffering from the same disease the baby is suffering from) and both work to correct the problem.
Other storylines involved in the crossover include Derek's mother hating Addison, Addison helping Bailey with her pediatric surgery fellowship application, and the debate over whether Sam is having a simple asthma attack or a panic attack about Naomi.
==Bailey's Patient Crossover, October 2009==
*Episode: Right Here, Right Now (PP)
*Character Crossing Over: Miranda Bailey
Coming off the heels of the successful February 2009 crossover, a further crossover was planned for the start of the 2009-2010 television season. This was the first crossover to take a more patient-centered approach as the crossover followed the attempts of Miranda Bailey's patient Sarah to receive a kidney transplant. The crossover began in the Grey's Anatomy episode "Invasion" where Bailey organized a kidney transplant for Sarah, only for Izzie Stevens to incorrectly read her chart and give her to the wrong medication making her transplant impossible. Bailey then headed to Los Angeles with Sarah, where her sister and a possible donor, lived and Addison and the Oceanside Wellness Group helped Bailey find her a transplant while, in Seattle, the ramifications of Izzie's mistake led to her being fired.
In the Private Practice episode "Right Here, Right Now", Addison and Sam became involved in the case which was complicated when Sarah's sister tested HIV positive, making Addie, Sam and Bailey question the ethics of the situation. After twisting the arm of Charlotte, Bailey and Sam perform surgery on Sarah and give her her sister's kidney. This crossover allowed Sam to return to surgery (which would become important in the following episode "Pushing the Limits") and also showcased the end of the flirtatious relationship between Sam and Bailey established in "Ex-Life", during the previous crossover.
In regards to this crossover, "Invasion" isn't regarded as part of the crossover as this episode introduced the patient who only later crossed over with Bailey.
==Sloan's Daughter Crossover, January 2010==
*Episodes: Blink (GA) and Another Second Chance (PP)
*Characters Crossing Over: Addison Forbes Montgomery and Mark Sloan
The second crossover of Season Six, and also the second patient-centered crossover. The scene is set for this crossover in Holidaze, where Mark Sloan discovers he has an 18 year old daughter who is carrying his grandchild. In the first part of the crossover, Lexie performs an ultrasound on Sloan Riley, Mark's daughter, and discovers something concerning: bands of amniotic tissue were wrapped around the fetus' legs. Upon learning that no one at Seattle Grace is qualified to deal with the situation, Mark calls in Addison from L.A. to perform the surgery. However, when Addison and Sloan were in surgery, it was gets complicated due to Sloan's uterine arteries being enlarged and getting in the way. Addison tries to convince Sloan she can handle the risky procedure, but Sloan made her "shut it down."
Later realizing he has made a mistake, Lexie suggests that Mark take Sloan to L.A. for Addison to do the surgery there, and Mark agrees. After Mark says that Sloan may live with him after the baby is born, he and Lexie break up, as she cannot deal with being a grandmother yet. Mark asks Lexie not to make him choose between her and Sloan, because Sloan will win, so he and Lexie break up.
In the second part of the crossover, Mark takes Sloan to the Oceanside Wellness Group, so that Addison can perform the operation she was supposed to do in Seattle. Within minutes of arriving, Mark gets Addison naked, and they 'do the McNasty' in Addison's office. Addison performs the surgery successfully. Mark deliberates staying in L.A. to work with Addison, Sam, Naomi and the others, but in the end Addison convinces him not to, because he still loves Lexie.
==Amelia's Crossover, October 2010==
*Episodes: Superfreak (GA)
*Characters Crossing Over: Amelia Shepherd
This crossover took yet another different spin, this time looking at the brother-sister relationship of Derek and Amelia. It also looked at Derek's growing relationship with Cristina after she saved his life at the end of Season 6 during The Shooting. There was also an element of the patient-centered setup as seen during the last two crossovers, as the other elements revolve around the case. However, this is a much weaker feature than before, with the main focus being on the first two features.
The crossover begins in the Private Practice episode "Short Cuts", when Addison pushes Amelia to fly to Seattle to reconcile with estranged brother Derek. Amelia does so, bringing with her a man that she met on the plane who she suspects might have a brain tumor, though this is only because he had pudgy hands which Derek discovered she found out because the man "had his hands on her breasts at the time" and it was a "mile-high hookup." Amelia convinces Derek to admit the patient, and puts Cristina on the patient, as he is currently trying to help her overcome her fear of the O.R. following her recent trauma of saving Derek's live with a gun to her head (for more information, see Death and All His Friends).
When looking at scans of the brain surgery patient's head, Cristina refuses to give any ideas about how to approach it, leading Amelia to believing that she is an incapable surgeon, saying, "why don't we just shoot the guy now?" which Derek takes immediate offense to, saying, "don't talk about shooting people in this hospital." Amelia wants to scrub in, and Cristina is more than willing to let her, but Derek won't let it happen and demands that Cristina book an O.R., which she does, but unwillingly.
Derek then explains to Meredith how Amelia was a drug addict, and how she stole his prescription pad to write herself a prescription for pain pills before crashing his car and overdosing, forcing him to save her. As Derek and Amelia are scrubbing in for the surgery, Amelia confronts Derek about how he won't talk about his own shooting or her father's, which happened when she was 5. Cristina shows up to the surgery late and Derek relents, allowing Amelia to scrub in.
Derek continues to try to push Cristina to help out with the surgery, but in the end gives up as she refuses to help out, allowing Amelia to step in. After the surgery, Cristina asks, "can I go now then?" and Derek allows it. Amelia calls Cristina "a dud," and Derek gets angry and kicks her out after saying that Cristina saved his life and he owes her "everything." He then brings Cristina to a cadaver and walks her back through the process of how she operated on him. He forces her to take a scalpel and do it again. She hesitates, then makes the first cut. He asks what happened next and she continues the process, slowly regaining confidence.
Derek meets up with his sister outside the hospital and tells her the story of when their father was shot. As he tells her the story, she recalls trying to move toward her dad, "but I couldn't move." He told her he was holding her so tight she couldn't budge. He also tried to keep her quiet as the men left. "You were so little," he says, adding that he's probably always wanted her to remain "the little one -- quiet and safe." But she's neither. She's "loud and fearless and it scares the crap out of [him]." He says he didn't want to tell her he'd been shot because he didn't want her to know that pain exists. Amelia then returns to L.A., now on speaking terms with her brother again.
Like "Invasion" in regards to Bailey's Crossover, "Short Cuts" is not regarded as part of this crossover.
==Grey's Anatomy: The Music Event, March 2011==
* Episodes: Song Beneath the Song (GA)
* Characters Crossing Over: Addison Forbes Montgomery
Addison crosses over to help save Callie and her unborn baby's life. Callie and Arizona get into a car accident when Callie is 23.5 weeks pregnant. Originally Lucy is in charge of monitoring Callie's pregnancy, but admits she is "out of her depth" when questioned by Richard in the OR. Addison arrives on a chopper part way through the episode after a phone call from Richard. Addison later performs an emergency C-section on Callie and delivers her daughter, Sofia Robbin Sloan Torres, prematurely.
==Finding a Cure for Erica, February 2012==
*Episodes: Have You Seen Me Lately? (GA) and You Break My Heart (PP)
*Characters Crossing Over: Amelia Shepherd, Derek Shepherd and Lexie Grey
Amelia crossed over to consult with Derek on Erica's case. Driven by the thought of saving Mason's mother, Amelia managed to come up with a difficult neurosurgical procedure to try. Adding to the diffulty of the procedure itself, it had to be completed within 90 seconds or Erica would stroke out on the table. Therefore, Amelia asked Derek to help her out. After practicing all day long in the skills lab, they finally managed to pull it off within the 90 seconds, and Derek allowed Amelia to call Cooper to bring Erica over to Seattle.
Derek and Amelia successfully pulled off the procedure and this strengthened their bond. Amelia and Derek talked about Amelia's addiction after the surgery, with him offering to fly to LA every time she started craving some pills to knock some sense into her. She on the other hand felt more for remembering the successful procedure they just did and thereby having saved Erica's life.
Cooper, Charlotte, and Mason accompanied Erica to Seattle Grace Mercy West Hospital, but since they did so in the episode airing under Private Practice credits, they are not considered having crossed over from one show to another. 
==Addison's Uterine Transplant, October 2021==
* Episodes: Hotter Than Hell (GA) and With a Little Help From My Friends (GA)
* Characters Crossing Over: Addison Forbes Montgomery
Dr. Addison Montgomery came to Grey Sloan Memorial Hospital to help teach the struggling residents of Grey Sloan after the COVID-19 pandemic. She also worked with Dr. Amelia Shepherd and Dr. Meredith Grey on her uterine transplant trial, as she operated on Tovah Freedman.
Addison also got to meet Derek and Meredith's three kids after having a heart-to-heart conversation with Meredith Grey in the elevator after they operated on Tovah together.
Addison revealed she is still with her husband, Jake (who has a model train hobby) and they are still living together as a family with her video-game obsessed son. While talking to Amelia, Addison revealed she was in a dark place during the pandemic and had also been drinking.
Addison, before leaving Grey Sloan, talked again to Amelia and appreciated how Amelia was now all grown up.
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Category:Grey's Anatomy Universe