While in the containment unit, Slimer encounters spirits that the Ghostbusters had previously captured during the course of the show. These include Ghash from Slimer, Come Home (1986) and Precious from Mrs. Roger's Neighborhood (1986).
When the Stay Puft Marshmallow Man gets stuck between two buildings, Peter says "And here we are a bunch of fluffernutters". A fluffernutter is a sandwich made with peanut butter and marshmallow creme.
The voice actors were recorded on May 27, 1987.
Even though the Phantom flashes back to his moment of capture when he sees Slimer in the containment unit, this is his first screen appearance. No prior episode saw the Phantom's capture.
The Ecto-1's water raft addition is used again when the Phantom throws it into the New York Harbor.