Slimer was first seen pigging out at a hot dog cart. When the Ghostbusters witnessed the thing, he took control of the Ecto-1. He left the scene driving through the Hot Dog Stand and cause more damage. Slimer later was seen with Lady Slimer and the Ecto-1 Party Specters as they passed by the Ghostbusters in front of The Mercado building in the Times Square area. He and his crew were seen again as the Ghostbusters guided the Ecto-1 to go in the portal. Slimer along with his buddies end up going through the portal and the Divide to the World of the Dead.
Paul Feig and Katie Dippold came up with a backstory that Slimer was a gangster executed for killing a waiter who screwed up his order. Slimer started out as a "more traditional" ghost, but was disfigured when the Ghostbusters were called to the restaurant he was haunting. The equipment was still in the testing phase so the proton streams blew Slimer's legs off and turned him green. He distorted and becomes the Slimer seen in the movie then escapes the scene. The backstory idea was not used.   Tully Summers did designs for the Old Gangster Ghost on February 24, 2015. Slimer would emerge from it when the ghost was sliced by the Proton Stream.  Summers then worked on a sixth version of Slimer on February 25 to 26, 2015. The original design was going to be more alien-like and would have dangling entrails and it ate everything with rows of revolving teeth. Production ultimately scrapped the idea and went with a more classic look. 
It was decided Slimer would be a fully articulated puppet augmented with special effects.  The puppet was built and operated by Rick Lazzarini, who worked on Ghostbusters II.  The VFX teams at Sony Pictures Imageworks and MPC worked on Slimer.  Effects added random bits of hair in random places as well as an overabundant amount of slime so that it poured off Slimer's arms. 
- Slimer is loosely based on actor John Belushi, which was close friends with Dan Aykroyd.
- Slimer also was in a hot dog stand in Ghostbusters (1984 movie).
- Slimer also drove a bus in Ghostbusters II, much like him driving the Ecto-1.
- On April 11, 2016, Adam Ray announced he was the voice of Slimer. 
- There was some debate about putting Slimer in the trailer or not. Once Paul Feig saw special effects for him, Feig decided it was okay to put him in it. 
- Slimer makes a non-canon cameo on Credits Page of Ghostbusters 101 #1.
- On the Subscription Cover of Ghostbusters 101 #5, on the right bottom is Slimer.
- Ghostbusters 101
- ↑ Wired "At Last: The Untold Backstory of Slimer From Ghostbusters" 7/15/16 Line reads: "According to Feig, who created a backstory with Ghostbusters co-writer Katie Dippold, Slimer was a gangster executed for killing a waiter who screwed up his order. Slimer started his afterlife as a more traditional ghoul, but was disfigured when the Ghostbusters were called to the restaurant he was haunting."
- ↑ Wired "At Last: The Untold Backstory of Slimer From Ghostbusters" 7/15/16 Paul Feig says: "When the Ghostbusters come in, they haven't quite tested their equipment yet, so they haven't got the levels right. The proton beams are too hot, so it blows his legs off. Then it turns him green. He starts to distort, and so he becomes Slimer. Then he escaped out into the world."
- ↑ Tully Summers "Ghostbusters: Gangster Ghost" Artstation 1/2/18 Tully Summers says: "This one was interesting. He starts off a gangster ghost in a speak easy, leaking green from where he was tommy gunned to death. The Ghostbusters cut him in half with their proton packs, and it's revealed he has an otherworldly Slimer ghost hiding within the human shell."
- ↑ Tully Summers "Ghostbusters: Otherworldly Slimer" Artstation 1/2/18 Tully Summers says: "This was my Slimer redesign back when the ghosts were more alien. He's intended to break out of the Gangster ghost. Sliming everyone with his dangling entrails and eating everything with rows of revolving teeth. Production eventually decided to go with the good old classic design from the first film."
- ↑ Empire Online "Ghostbusters - trailer breakdown with Paul Feig" 3/9/16 Paul Feig says: "But again, the thing with Slimer is we had a fully articulated Slimer puppet we used, and then we augmented him with special effects."
- ↑ Semlyen, Nick (2016). Empire Magazine Issue 324 June 2016, p. 64. Bauer Media Group, Harborough, Leicester, United Kingdom, ISBN 1234567890. Line reads: "The new movie combines old technology (a fully articulated Slimer was built and operated by Ghostbusters veteran Rick Lazzarini) with new (CG augmentation) to create the most disgusting and deranged version yet."
- ↑ Semlyen, Nick (2016). Empire Magazine Issue 324 June 2016, p. 64. Bauer Media Group, Harborough, Leicester, United Kingdom, ISBN 1234567890. Line reads: "In the end the coveted job went to Sony Pictures Imageworks and MPC."
- ↑ Semlyen, Nick (2016). Empire Magazine Issue 324 June 2016, p. 64. Bauer Media Group, Harborough, Leicester, United Kingdom, ISBN 1234567890. Paul Travers says: "We added random bits of hair in random places, like he's an old person. And we've added a bunch of goopy slime to him, just pouring off his arms I mean he is called Slimer."
- ↑ adamraycomedy Tweet 4/11/16
- ↑ The Verge "Analyzing the Ghostbusters trailer with director Paul Feig and writer Katie Dippold" 3/3/16 Line reads: "People are obsessed with Slimer. He's probably the most recognizable thing from Ghostbusters, or the thing that people are most focused on. It’s so funny to me. Even Ivan will say that was just a side character. It wasn't really until the cartoons that it took on a life of its own. But we debated a long time, and I was really against putting him in this trailer in the beginning. Then as I saw the special effects come in — he's actually a puppet, and then we CG'd over him to make him more lifelike --- I thought, "Ah, we can put him in. He looks cool." You don't want to put anything out that you don't think is ready yet, but I thought he looked pretty fun."
- ↑ Abby Yates (2017). IDW Comics- "Ghostbusters 101 #3" (2017) (Comic p.11). Abby Yates says: "Is... isn't that the ghost that stole our car?"
- ↑ Jillian Holtzmann (2017). IDW Comics- "Ghostbusters 101 #3" (2017) (Comic p.11). Jillian Holtzmann says: "Nah. That one got blown up."