Entertaining episode but with a illogical plot. The Ghostbusters get caught in a magic wind storm that sends them back to the 1800's. Here they meet Ebenezer Scrooge (they don't know it's him even though it's obvious as the Three Spirits of Christmas are around him).
They accidently trap the Three Spirits of Christmas past and Christmas doesn't become the special time it is. Instead, Scrooge writes "Hum-Bag" putting down Christmas and Christmas is never the same.
As mentioned silly plot, but we do get a hint about Peter Venkman's past including his Dad (who comes in Season 2).
The look inside the ghost facility was also a first as well. Later on the series, viewers would get more looks inside the containment unit. Overall, a decent episode, they did add a Christmas like story at the end of the first season to make it stand out from the other episodes.