The series was originally developed as a direct adaptation of Daniel Keyes' 1981 nonfiction novel The Minds of Billy Milligan, but it was later revealed that the season is actually based on creator Akiva Goldsman's own life, only inspired by Keyes' book.

Tom Holland's role was initially believed to be a portrayal of Billy Milligan himself, but it was later revealed his character, Danny Sullivan, is a fictional character only loosely based on Milligan.

Creator Akiva Goldsman said Tom Holland was 'the first and only person' he approached to play the lead role of Danny Sullivan.

Akiva Goldsman, the show's creator, also appears in the series himself in a guest role as 'Doctor'.

Principal photography began on March 31, 2022, in New York City and wrapped on September 28, 2022.

One of the notable filming locations used for the series was NBC Studios at the historic 30 Rockefeller Plaza.

The series received negative reviews from critics, holding a 34% approval score on Rotten Tomatoes and a Metacritic score of 48 out of 100, indicating mixed to negative reception despite its cast.