There was very little information made available about the character ahead of his debut.
Cohen's casting came on the heels of the soap losing one of its longtime leading men Jason Thompson in the role of Dr. Patrick Drake, and the character's introduction would help replenish the hospital.
It was announced that he would be debuting during the first week of February.
It was also revealed that he is the previously unknown son of Duke Lavery, who was conceived before Duke met Anna Devane. Griffin also stated that he didn't know who his father was until after his mother, Margaret Munro passed away (she wrote him a letter explaining everything).
He has also formed a friendship with Anna Devane.
As of April 15, 2016, it appears he also recognizes Det. Nathan West. On June 29, it was revealed that Griffin had an affair with Nathan's then-wife, Claudette and Nathan shot him in a drunken rage. On August 3-4, Claudette and Griffin unexpectedly reunited with each other at GH. It was also revealed that Claudette was and is still in love with Griffin and he is in love with her.
Dr. Griffin Munro first arrived in Port Charles in February 2016, having taken over the neurosurgery position vacated by Patrick Drake. After encountering Sonny Corinthos in the hospital chapel, he is soon assigned to become his doctor and discovers that Corinthos has been faking his paralysis for some time. After imploring Corinthos to come clean to his loved ones, Sonny tells Griffin that he needs for his enemies to see him as weak. Griffin agrees to Sonny's request under the condition that Sonny keep him up to date on his progress.
Following the accidental shooting of Kiki Jerome, the truth about Sonny's health comes to light, and Griffin ends up apologizing to Sonny's wife, Carly Corinthos for concealing the truth. Griffin is also tasked with informing Kiki's mother, Ava Jerome and Franco that Kiki may have limited mobility as the result of her shooting. Griffin is also introduced to Anna Devane by Lucas Jones, and it becomes apparent that Griffin shares a mysterious connection with Anna. Griffin is also on hand to treat Tracy Quartermaine after she suffers a seizure at The Floating Rib.
On March 15, 2016, Griffin revealed to Anna that he's Duke's son and he has since taken a DNA test that proved that he is Duke's son.
On May 24, 2016, he walked Maxie Jones down the red carpet and received a text from Emma Scorpio-Drake prior to the Nurse's ball.
Later in 2016, it was revealed that Dr. Munro is a suspect in the deaths of patients at the hospital but he is no longer a suspect.
He is also eventually revealed to be the man that Nathan's ex wife Claudette cheated on him with and that Nathan shot. On January 19, 2017, during Nathan and Maxie's wedding, Griffin gets a beat down from Valentin after he declaring he doesn't deserve his daughter Charlotte before being saved by Anna.
In March 2017, Griffin was kidnapped by his fathers thought to be dead ex-girlfriend, Olivia Jerome, who was obsessed with him. She tried to use Griffin to resurrect his father.
In late 2017, Griffin gets involved with Ava Jerome and eventually ends his relationship with the church (as a priest) to pursuit a relationship with her. In 2018, when Ava threatens to have Sonny's alzheimer father Mike Corbin arrested for unintentionally kidnapping Avery, Griffin begins to see see her in a different perspective and on May 7, he moves out of her apartment and moves into the Metro Court. Despite seeing him as the worst kind of hypocrite, Carly reluctantly allows him to stay at the hotel because she doesn't want him to go back to Ava.
On May 23, 2018, after the Nurses Ball, he and Kiki Jerome end up drunk and then soon end up having sex. The next morning, they agreed to keep their night a secret so they wouldn't hurt Ava.
↑On February 10, 2016, Griffin said he was a year older then Lucas in medical school. Lucas birth year was re-established as 1987 in 2005. Also, on March 15, 2016, Griffin tells Anna that he was born shortly after Duke came to Port Charles, which was in 1986.