@Woodman: Babylon 5 was a unique series in that the entire five-year storyline was plotted out before the pilot was even filmed, and even then, series creator J. Michael Straczynski said he didn’t have time in that five years to tell the whole story, so some of it went into about 20 novels (with some of them being three trilogies of stories), some comic books, a few stories in magazines and six TV movies, one of which led into the spin-off series Crusade. That one ended after 13 episodes due to severe executive meddling. He filmed the final episode for Babylon 5 at the end of season 4 when it wasn’t certain if they’d get that fifth year. They did get season 5, so he got to do the rest of the storylines he wanted and still kept the ending he planned on. He wound up writing 92 of the 110 episodes, including all of the ones for season 4, which I think are records that beat all other TV shows.
JMS also had contingencies in place for when actors wanted to leave the series. Each character had a backup. I think he said at one point that with a show where so many small plotlines built towards a greater story, it was pretty much required that he do this.
So for example, when Michael O’Hare decided to leave after the end of the first season, Commander Jeffrey Sinclair was replaced by Captain John Sheridan, played by Bruce Boxleitner. Michael came back an episode in season 2 and in a two-part episode that was a major event in season 3. What happened to Sinclair afterwards was told in one of the novels and was tagged by JMS as (paraphrased) “an official episode that we didn’t happen to film”.
It wasn’t until in 2013 and eight months after Michael died that JMS revealed the reason why he left the series. Michael had been having some mental health issues and it was starting to affect his ability to be an actor and how he interacted with the other cast members. So they both agreed he’d leave the show, and as mentioned, was able to come back three more times. During that conversation, JMS first promised to take Michael’s secret to his grave, but Michael corrected it to be “to my grave”. Michael got quite a bit better later on, but I think the only other acting he did on TV was the two episodes of Law & Order.
Another tidbit: JMS admitted that he kept a binder on the shelf behind his desk that contained the index cards with all of the plot points for the entire series. His computer was triple-encrypted, but that binder was in plain sight for several years. Then he took it with him to a convention because he had to also work on upcoming episodes for Season 5 and someone on the hotel’s cleaning staff threw it away. He searched the dumpsters but never found it. I forgot what he used for reference to write those episodes.
The guy put a lot of effort into the show and communicated freely with the fans at a time when no other show did that. It was also rare in that the stories that were in the comics, books and magazines were very close to being 100% canon since most of them worked from story outlines he wrote and handed off to those groups.
It’s a show that rewarded you for watching it and it’s why I’ve bought all of the reference material that JMS has published about the show during the past 10 years.