The River of Slime (also known as Psychomagnotheric Slime Flow) appears and is talked about in great detail in Ghostbusters II. Later in Ghostbusters: The Video Game, the River of Slime's origins and purpose are expanded upon.
Ghostbusters: The Video GameEdit
In the 1920s, the Cult of Gozer created a strain of Ectoplasm later known as Psychomagnotheric Slime. They pumped the slime past the Hudson River into New York City's decommissioned New York Pneumatic Railroad. It was intended to provide more power to Gozer upon its arrival.
Gozer never got the chance to draw power from the River of Slime. Five years after Gozer's defeat, the River came under the control of Vigo. He used the power generated from the negative emotions of New York City citizens to try and resurrect himself in the body of a child. Ray Stantz discovered the River but was almost pulled in. He later found it again on foot with Egon Spengler and Winston Zeddemore. When Winston tried to take a measurement, he was pulled in. Egon and Ray jumped in after him. They rode the flow of the river straight to the Manhattan Museum of Art.
A second river of Psychomagnotheric Slime running under Las Vegas stored the negative emotional energy of gamblers over the decades.  In the present, the ghost of stage magician Ethan Kaine tapped into the power stored in the River of Slime and transformed buildings along the Vegas Strip into skewed versions of the past. To make matters worse, Kaine's new powers also allowed him to act as a beacon and attracted a legion of ghosts to the city. Ray and Special Agent Melanie Ortiz followed his hunch and explored Las Vegas' network of tunnels where they found the River of Slime. Ray wired a canister of positively charged psychomagnotheric slime to a Proton Grenade and tossed it into the river. Kaine's connection to the river was destroyed but the resulting explosion also sent slime up into the fountains of the RKO Casino. The affected buildings suddenly began to return to normal except the Olive.  The RKO Casino's fountains were contaminated, fully drained, cleaned, and refilled. The casino demanded a $470,000 reimbursement from the Ghostbusters and the FBI. 
- In the Ghostbusters II August 5, 1988 draft, the River of Slime is not present. Instead, Ray and Egon fall into a slime pit full of bugs and rodents.  
- In NOW Comics The Real Ghostbusters starring in Ghostbusters II part 1 the river of slime along with the Psychomagnotheric Slime sample in the court room is green and not pink.
- In NOW Comics The Real Ghostbusters starring in Ghostbusters II part 2 and NOW Comics The Real Ghostbusters starring in Ghostbusters II part 3 it is suggested to be pink like the film.
- Chapter 08: Down the Shaft
- Chapter 09: Great Blackout of 1989
- Chapter 18: In the Tunnel
- Chapter 20: Kidnapping Oscar
- ↑ Spectral Incident Report (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.23). Spectral Incident Report reads: "The tunnels were overflowing with psychomagnatheric ectoplasm (AKA mood slime, see report 1410 for a rundown on the various types and of ectoplasm and their properties.) This mood slime stored a high amount of power from the emotional energy of gamblers, and Kaine was able to tap into it in a manner similar to that of Vigo the Carpathian (see form 11470H, filed by the New York field office)."
- ↑ Spectral Incident Report (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.23). Spectral Incident Report reads: "The buildings on the strip started to revert to normal, with the exception of the Olive, which remained transformed until Kaine's ghost was trapped by Kamaka and Shpak."
- ↑ Spectral Incident Report (2016). IDW Comics- "Ghostbusters International #7" (2016) (Comic p.23). Spectral Incident Report reads: "The fountains of the RKO Casino (a closed system) were contaminated and required a full draining, cleaning, and refilling, which cost $470,000. The casino is demanding reimbursement from the Bureau and Ghostbusters for this."
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 63). Paragraph reads: "Their skin and clothing are caked with mashed bugs and some sort of foul muck."
- ↑ Aykroyd, Dan & Ramis, Harold (1988). Ghostbusters II (August 5, 1988 Draft) (Script p. 64). Ray Stantz says: "I fell into a slimepit full of bugs and rodents. Spengy had to pull me out."