The song that Ally chooses as her "theme song" is "Tell Him" by Bert Berns, it is used extensively in the show from hereon.
The first "theme song" that Ally sings to her therapist is "Searchin' My Soul", which is actually the song that is played during the opening credits of the show.
The plot of a doctor using a a pig's liver as a transplant may sound far-fetched. However, in 2022, a surgeon transplanted a genetically modified pig's heart into a human patient in a last-ditch effort to save his life.
Ally chose the series theme song 'Searchin' my Soul' as her first theme song. When her therapist Tracey responded with 'Stinks!' the songwriter and performer of that song, Vonda Shepard actually laughed.