The yellow Oldsmobile Delta 88 that Ash drives is the same make, model, and color used in most of the movies directed by Sam Raimi. The original car belongs to Raimi, and was bought new by his father in 1973.
Army of Darkness (1992) didn't get a sequel for a long time because it had bombed commercially, but after becoming a cult movie over the years and the success of the remake Evil Dead (2013), a fourth Evil Dead movie was officially in the works. Ash vs Evil Dead was originally meant to be that movie, but due to so much material being written and the relative ease of securing budget for television rather than film, the makers decided to turn it into a TV series instead. If the first season was a movie, it would've been around five hours long.
It was given approval of a second season three days before it premiered on Starz on October 31, 2015.
Sam Raimi originally intended to follow Army of Darkness (1992) with a fourth Evil Dead movie. The plan was to continue both the ending of the theatrical cut of the film (where Ash returns home from the Middle Ages) and the director's cut (where Ash inadvertently ends up in a post-apocalyptic future) with a film that followed two different timelines simultaneously. The concept was eventually abandoned, due to its complex nature.
The songs that appear in the series' soundtrack are all from the 1970s and 1980s and were picked by Sam Raimi and Rob Tapert because they believed they would be songs that Ash listened to back before his first demonic encounter in the cabin and symbolized his lack of growth since that night, with Raimi stating "the music should reflect the last time he was engaged in society, and living."