*Cover A
**Appearing on the cover are Slimer from The Real Ghostbusters, Rookie piloting Kenner's Ecto Bomber, Roland Jackson from Extreme Ghostbusters, and Janine with the Compact Pack.
*Cover B
**The cover is a nod to on when the Spectral Ghostbusters marched into the Firehouse in The Real Ghostbusters episode "Citizen Ghost".
**The Spectral Ghostbusters on this cover are doppelgangers of:
***Eduardo Rivera from Extreme Ghostbusters
***Janine Melnitz from Prime Universe
***Ron Alexander from Prime Universe
***Jillian Holtzmann from Answer The Call
**The Spectral Janine has the Tease Ray weapon from the Kenner Fright Feature Janine figure.
**Spectral Ron has on the Ghost Smashers uniform and totes the Proton Bazooka.
**Left of Spectral Eduardo is the city map from the Activision Ghostbusters game from 1984.
**Right of Spectral Holtzmann is the box of contaminated flightsuits and from The Real Ghostbusters episode "Citizen Ghost" and the note references Egon's urging to destroy it that Peter ignored.
*Cover RI
**Rachel Unglighter from the Displaced Aggression mini-series is featured, as the cover artist is that mini-series' artist, Ilias Kyriazis.
*What Came Before
**Mentioned are:
***Ron meeting Holtzmann in Ghostbusters Annual 2018.
***Having a teleportation unit by Ghostbusters Crossing Over Issue #1.
***The explosion at the end of Ghostbusters Crossing Over Issue #1.
***The Containment Unit
***The "Spirit Guide" Peter and Jenny met in Ghostbusters Crossing Over Issue #2.
*Dramatis Personae Page 1
**The Prime Ghostbusters' bio mentions:
***Gozer
***When they crossed the streams at the end of the first movie.
***Seeding the multiverse, which as discussed in Ghostbusters 101 Issue #3.
**The Chicago Ghostbusters' bio mentions Chicago's Windy City nickname.
**The New Ghostbusters' bio mentions the events of Ghostbusters Volume 2 Issue #1.
**The New Ghostbusters' bio alludes to The Collectors.
**The images used for the characters are:
***Peter from Ghostbusters Crossing Over Issue #1, page 18, panel 2.
***Ray from Ghostbusters Crossing Over Issue #1, page 4, panel 4.
***Egon from Ghostbusters Crossing Over Issue #1, page 5, panel 1.
***Winston from Ghostbusters Crossing Over Issue #1, page 9, panel 2.
***Ron from Ghostbusters Crossing Over Issue #1, page 1, panel 5.
***Rookie from Ghostbusters Crossing Over Issue #3, page 9, panel 4.
***Dani from Ghostbusters Crossing Over Issue #3, page 9, panel 1.
***Lou from Ghostbusters Crossing Over Issue #3, page 9, panel 1.
***Janine from Ghostbusters Crossing Over Issue #1, page 12, panel 5.
***Melanie from Ghostbusters International Issue #4, page 11, panel 4.
***Kylie from Ghostbusters Crossing Over Issue #1, page 8, panel 5.
***Garrett from Ghostbusters 101 Issue #2, page 13, panel 6.
***Cait from Ghostbusters 101 Issue #1, page 12, panel 5.
***Zoe from Ghostbusters 101 Issue #1, page 12, panel 3.
***Evan from Ghostbusters 101 Issue #1, page 12, panel 3.
*Dramatis Personae Page 2
**The Answer The Call Ghostbusters' bio alludes to Rowan North.
**Patty's last name is misspelled "Nolan" instead of "Tolan"
**The Real Ghostbusters' bio alludes to meeting the Prime Ghostbusters in Ghostbusters Get Real.
**The Extreme Ghostbuters' bio mentions their Egon Spengler.
**The Support Staff section lacks a "(Prime Universe)" like the others did on the first page.
**The images used for the characters are:
***Abby from Ghostbusters 101 #1, page 20, panel 4.
***Erin from Ghostbusters 101 #1, page 20, panel 1.
***Holtzmann from Ghostbusters 101 #1, page 17, panel 2.
***Patty from Ghostbusters 101 #1, page 16, panel 3.
***Kevin from Ghostbusters 101 #1, page 19, panel 3.
***Egon from Ghostbusters Crossing Over #2, page 20, panel 2.
***Winston from Ghostbusters Crossing Over #2, page 20, panel 2.
***Ray from Ghostbusters Crossing Over #2, page 20, panel 2.
***Peter from Ghostbusters Crossing Over #2, page 20, panel 2.
***Eduardo from Ghostbusters Crossing Over #3, page 4, panel 2.
***Kylie from Ghostbusters Crossing Over #3, page 4, panel 2.
***Garrett from Ghostbusters Crossing Over #3, page 4, panel 2.
***Roland from Ghostbusters Crossing Over #3, page 4, panel 2.
***Samuel from Ghostbusters Crossing Over #3, page 3, panel 4.
***Alan from Ghostbusters Crossing Over #3, page 3, panel 2.
***Bridget from Ghostbusters Crossing Over #3, page 3, panel 4.
***Gabriel from Ghostbusters Crossing Over #3, page 3, panel 2.
***Walter Peck from Ghostbusters Crossing Over #1, page 13, panel 1.
***Jenny Moran from Ghostbusters Crossing Over #1, page 18, panel 2.
***Kevin Tanaka from Ghostbusters 101 #2, page 10, panel 5.
*Page 1
**The second panel reuses the second panel from page 20 of the previous issue.
*Page 2
**Peck's visitor estimates there are less than 50 Ghostbusters at the Warehouse. There are 45 to be exact. 48 if Kevin Tanaka, Kevin Beckman, and Jenny Moran are counted.
**Peck's pours from a bottle that references Kildarby from The Real Ghostbusters episode "The Bird of Kildarby".
***The Kildarby is a stand-in for Jameson.
***The Kildarby name was first used as the name of an alcohol brand back in Ghostbusters International #1, on page 15, as one of the four leaf clover neon display outside O'Shaner's.
**The frame left of Peck is a photo of Peck meeting President Reagan in the Oval Office.
**Peck asks how many Peter Venkmans there are. There is the Prime Peter and 5 from other dimensions.
*Page 3
**In panel 1 is the ionized enclosure's panel. It was used by Egon in Teenage Mutant Ninja Turtles/Ghostbusters Volume 2 Issue #3.
**Peck's visitor summarizes the events of Ghostbusters Crossing Over Issue #1 and #2.
***The Containment Unit is mentioned.
***The Interspatial Teleportation Unit is alluded to.
**Gabriel and Bridget allude to the DC Comics superhero The Flash and more specifically, the current live action television series on the CW network.
**Samuel appears to reveal their encounter with Proteus' Cerberus manifestation in Ghostbusters Get Real Issue #3 was six months ago.
*Page 4
**Ray once again refers to the unit as the Transdimensional Portal as it was in The Real Ghostbusters episode "The Copycat".
**Extreme Ghostbusters Kylie mentions their team's Egon and it is pointed out he's an older version of the Real Ghostbusters one.
**The Sanctum of Slime Ghostbusters takes place in the 2010s give or take.
**Gabriel mentions Dumazu, the principal villain of the Sanctum of Slime video game.
*Page 5
**Peter mentions when they met their future selves in Ghostbusters Volume 2 Issue #16 in the stairwell of Dana's current apartment building and that Egon's weight gain.
**Peter was in a coma for most of Ghostbusters Crossing Over Issue #2.
**Egon mentions some dimensions are further ahead like the Sanctum of Slime Ghostbusters as well as the Answer The Call Ghostbusters, who are from 2016 in their movie and about 2017 in the 101 mini-series. The Real Ghostbusters are from the mid-late 1980s.
*Page 6
**In panel 3, on the face of Melanie's phone is ?
**Peter addressed Holtzmann's ADHD in Ghostbusters 101 #4.
*Page 7
**Peck's visitor mentions Chicago.
*Page 8
**Melanie refers to the FBI having its own research department for her cases. In Crossing Over #1, the departmental memo mentions Melanie's assignment is formally known as the Paranormal Response Task Force.
**Melanie mentions author Stephen King and Maine, alluding to "The Mist".
*Page 9
**Holtzmann refers to Lou and Dani as Daphne and Velma, two of the lead characters from "Scooby-Doo".
**Holztmann is wearing her headset from the end tags of the 2016 movie.
**Lou mentions the Hudson River.
**Melanie alludes Light 80, the "Little Red Lighthouse."
**Winston mentions Mars.
**Holtzmann plays Marco Polo.
*Page 10
**The Laws of Attraction are mentioned. It is from the New Thought philosophy widely seen as a pseudoscience.
**The ghost's fog form is visually based on The Thing from The Real Ghostbusters episode "The Thing In Mrs. Faversham's Attic".
*Page 12
**In panel 1, on the bottom middle of white board is "Dave L" a nod to Dave Laenen, a member of the Ghostbusters of British Colombia. He supplied Schoening with a fair amount of the equations on the board.
*Page 13
**Holtzmann alludes to actor Sean Connery.
*Page 16
**In panel 4, on the POV screen of Holtzmann's goggles are:
***Luis Delgado's 15 easter egg.
***1967 refers to Leslie Jones' birth year.
***01061984 refers to Kate McKinnon's birth date, January 6, 1984.
***07152016 refers to July 15, 2016, the date the 2016 movie came out in theaters.
***KM is Kate McKinnon's initials.
***On the upper right is the screen used for Kenner's The Real Ghostbusters P.K.E. Meter, but without the ghost icon.
*Page 17
**The ghost's true form is revealed. It is one of the ghosts who yelled Doom! at Ron in Annual 2015 "Just a Peek".
*Page 18
**In panel 3, once again, the portrait of the woman in yellow is Anne Gorsuch Burford, the head of the EPA in the Reagan Era.
*Page 19
**Egon alludes to when the Trapgate was used to capture Darius Dun and the Collectors in Issue #5 of Teenage Mutant Ninja Turtles/Ghostbusters Volume 2.
**In panel 1, Extreme Ghostbusters Slimer is eating from a bag of Wise Potato Chips from the first movie.
**In panel 2, Dani is reading Creature magazine from the Slimer and The Real Ghostbusters intro.
***The back cover is the ad for The Real Ghostbusters Potato Snacks.
**Abby's concern about the 101 interns is warranted as they caused the Dimensional Bleed incident in the Ghostbusters 101 mini-series.
**In panel 4, Kevin is wearing his white T-shirt from when he was possessed by Rowan in Chapter 13 of the 2016 movie.
*Page 20
**Patty mentions finally starting a book club. In the 2016 movie, during the Stonebrook Theatre case, Patty muttered to herself she thought the Ghostbusters was just a book club.
**Kevin Beckman thinks about growing long hair, a nod to Chris Hemsworth who portrays Thor in the Marvel Cinematic Universe movies.
**In panel 4, Kevin is now inexplicably wearing his brown coat from Chapter 8 of the 2016 movie.
*Page 21
**The narrator alludes to the conclusion of Volume 2 Issue #20 when Tiamat took away the world's memory of Winston and Tiyah getting married and left only Winston able to remember it.
*Page 22
**The 35-N designation was first revealed by Tom Waltz in a tweet on May 10, 2018 promoting Crossing Over #4.
**Kylie first mentioned Peter's trips to see the undefeated New York Jets in Ghostbusters 101 #1.
**Mentioned in the memo are:
***Peter
***Brownies from Scottish folklore
***Kobolds from German folklore
***Hobs from English folklore
***Sedgewick Hotel
***Slimer
***Mike the Golem
**The Slimer sprite's name, Jim. It wasn't meant as a nod to Jim Belushi, just a funny contrast to the other names
*Page 23
**Cover A of Issue #4 is shown for the first time.
To Be Verified/Identified
1. Page 6: In panel 3, on the face of Melanie's phone is just a location alert?
2. Page 7: In panel 4, Melanie's license plate 072512-V3 is from anything?
This Post Contains Spoilers