Len Janson and Chuck Menville assigned Pamela Hickey and Dennys McCoy to write a Halloween episode. Around the time, there were a lot of horror movie sequels thus "Halloween II 1/2" was written.
In 2011, Matty Collector released a Retro-Action The Real Ghostbusters action figure 2-pack that featured Samhain and Janine Melnitz (in Ghostbusters outfit) as part of the 25th anniversary celebration of Ghostbusters (1984).
This marks the return of Samhain's two goblin minions. Some of the few spirits the Ghostbusters battle more than once.
This episode marks the return (second appearance) of Samhain. He is one of the few spirits that the Ghostbusters battle more than once. Samhain previously had a cameo appearance in the containment unit during the "Xmas Marks the Spot" episode and appeared as an illusion in "The Devil to Pay" episode.
Samhain received an entry in the 2016 tie-in book "Tobin's Spirit Guide - Official Ghostbusters Edition" on pages 68 and 69, where it is identified as a Class VII, with the ability to manipulate local environment and able to control lesser entities.