The “Babylon 5” cast had an unusually high turnaround rate, with only half of the principal actors from the pilot movie remaining for the entire series. Most surprising was the departure of the show’s original leading man, Michael O’Hare. After the end of the first season in 1994, series creator J. Michael Straczynski announced to fans on their Usenet message board that O’Hare would be leaving the series on friendly terms. His character, Commander Jeffrey Sinclair, was written out of the series, returning for a brief cameo in Season 2 and a two-episode arc one year later to wrap up some threads left dangling by his departure. Otherwise, he was replaced on the series by Bruce Boxleitner as the new Captain John Sheridan.
After O’Hare’s death from a heart attack in 2012, Straczynski revealed the hidden details behind O’Hare’s departure from the show. During production of the first season, Straczynski (who has a bachelor’s degree in psychology) noticed that O’Hare had begun to suffer from paranoid delusions on set and that his condition was worsening due to the stress of shooting the series. O’Hare and Straczynski worked together to try and keep the show on the rails for the rest of the season, but it was clear that O’Hare’s mental health was in serious jeopardy. In an effort to save the show, protect O’Hare’s career, and ensure he could get the help he needed, Straczynski wrote Commander Sinclair off the show and helped O’Hare get treatment for his condition during his absence from the series. This absence turned out to be permanent.
Straczynski offered to keep O’Hare’s secret to his grave, to which he says O’Hare replied, “Take this to my grave,” granting Straczynski permission to share his story should he predecease him.