Being a Massive Multiplayer Crossover, this series has multiple cameos, and even Cameo Cluster a good number of times.
- Heroes coming together:
- Chapter 2 has cameos by The Ancient One, Thanos, The Other, and the Senior Partners, who all react to the Singularity. Missouri Moseley also makes a brief appearance, telling Sam and Dean what she felt from the Singularity.
- Chapter 3 shows multiple breach cameos when Aragorn falls through a breach:
- Spider-Man/Peter Parker from Spider-Man (Insomniac).
- Scott McCall from Teen Wolf.
- Geralt of Rivia from The Witcher.
- Batman/Bruce Wayne from Batman: Arkham Series.
- Galen Marek from Star Wars: The Force Unleashed.
- Buffy Summers from Buffy the Vampire Slayer.
- L from Death Note.
- Lord Shiva from Shiva Trilogy.
- Jason Voorhees from Friday the 13th.
- We get more breach cameos when Ethan Hunt jumps through a breach:
- The Avengers from The Avengers: Earth's Mightiest Heroes.
- The Justice League from DC Animated Universe.
- Dante from Devil May Cry.
- Optimus Prime from Transformers Aligned Universe.
- The Tardis from Doctor Who.
- Guts from Berserk.
- Greek Kratos from the Greek Saga of God of War.
- Godzilla from MonsterVerse.
- Anakin Skywalker from Star Wars.
- Chapter 4 has a cameo by The Powers That Be from Angel. They are also original characters, since except Jasmine, a fallen Power That Be, none of them appeared individually in canon. Their names here are- Balial (the ruler of the Powers That Be), Behmen, Nigue, Jossetta Whedonasta (clearly meant to be an unflattering fictional Expy of Joss Whedon), Talzin and Vasoros (who is said to be the one who gives Cordelia her visions).
- Chapter 5 has more breach cameos when Blade falls through a breach:
- Son Goku from Dragon Ball.
- Harry Potter from Harry Potter.
- The Charmed Ones Piper Halliwell, Phoebe Halliwell and Paige Matthews from Charmed (1998).
- Raiden from Mortal Kombat.
- Ghostface from Scream.
- Cloud Strife from Final Fantasy VII Remake.
- Naruto Uzumaki from Naruto.
- Connor MacLeod and The Kurgan battling from the end of the 1986 Highlander movie from Highlander.
- Aslan from The Chronicles of Narnia.
- Yoda from Star Wars.
- Chapter 6 has brief appearances by Nathan Ford and Sophie Devereaux as well as Luther and Benji. It also has the Avengers, Clark and Bart facing off against a Tonberry.
- Art the Clown cameos in Chapter 7 and is dealt with by John Constantine. Curtis Holt also has a brief cameo in which he is killed by Chucky. Alice Pierce and Kyle also cameo.
- Chapter 8 has breach cameos once more when Angel and Buffy Summers fall through a breach:
- The Doom Slayer from Doom (2016).
- Asura from Asura's Wrath.
- Bayonetta from Bayonetta.
- Ryu in his Whelp Form from Breath of Fire III.
- Lelouch vi Britannia from Code Geass.
- Edward Elric from Fullmetal Alchemist.
- The Originals Klaus Mikaelson, Rebekah Mikealson and Elijah Mikaelson from The Originals.
- Snow White/Mary Margaret Blanchard from Once Upon a Time.
- Monkey D Luffy from One Piece.
- Castiel from Supernatural.
- Chapter 10 has cameos by Pinhead, Dante Alighieri and The Creeper.
- Chapter 11 has some picture cameos when Zemo shows pictures of various creatures to Lex Luthor:
- A Hel-Walker from the Norse Saga of God of War.
- A Tonberry from Final Fantasy.
- A Fyarl Demon from Buffyverse.
- A Gundark from Star Wars.
- A Null Void Vulpimancer from Ben 10.
- Clark Kent/Superman from Smallville
- In the same chapter, Steve Rogers battles an Ogre, with help from Iceman and Colossus.
- Chapter 12 has some breach cameos once more when Aragorn, Batman and Harry Wells go through a breach:
- Connor Hawke/John Diggle Jr./Green Arrow III from the Star City 2046 episode of Legends of Tomorrow.
- Barry Allen/The Flash from The Flash (1990).
- Kara Danvers/Supergirl from Supergirl (2015).
- Jonah Hex from Legends of Tomorrow.
- Peter Maximoff/Quicksilver from the new timeline of X-Men Film Series.
- An Earth-2 version of Batman/Bruce Wayne from The Batman (2022).
- Chapter 14 has a cameo by Trish Walker in a certain music video of hers.
- Chapter 15 has some breach cameos when Sam and Dean end up going through a breach:
- Hellboy from the Hellboy (2004) movie.
- Spawn/Al Simmons from the Image Comics.
- Swamp Thing from Swamp Thing (2019).
- Master Chief from Halo.
- Bumblebee from Transformers Aligned Universe.
- The Super Mario Brothers Mario and Luigi from Super Mario Bros..
- Sonic the Hedgehog from Sonic the Hedgehog.
- Victor Crowley from Hatchet.
- Spike from Buffyverse.
- There are more breach cameos in this chapter when Eliot Spencer and Oliver Queen go through a breach:
- Batman/Bruce Wayne from The Batman.
- Spider-Man/Peter Parker from The Spectacular Spider-Man.
- John Wick from John Wick.
- Angel from Buffyverse.
- Finally, there are some more breach cameos when Clark Kent ends up going through a breach:
- The Witch-King of Angmar from The Return of the King.
- Mega Man from Mega Man.
- Avatar Aang from Avatar: The Last Airbender.
- Homelander from The Boys (2019).
- Omni-Man/Nolan Grayson from Invincible (2021).
- Metro Man from Megamind.
- Sahjhan from Buffyverse.
- This same chapter also has John Rambo going up against a Predator.
- Chapter 16 has a cameo by Alicia Masters, while the Avengers and the Fantastic Four battle Giganto and Tricephalous sent by the Mole Man.
- In Chapter 18, an Earth-3 Wally West and an Earth-3 Fiddler both cameo.
- Chapter 19 has some breach cameos when Clint Barton finds himself going through a breach:
- Kayako Saeki from Ju On/The Grudge.
- The Fantastic Four from Fantastic Four Duology.
- Kingdom Come Superman/Clark Kent from Superman Returns who appeared in Crisis on Infinite Earths (2019).
- Judge Dredd from Dredd.
- Ben Tennyson from the original continuity of Ben 10.
- The PowerPuff Girls Blossom, Bubbles and Buttercup from The Powerpuff Girls (1998).
- Lord Krishna and Arjuna from Mahabharat 2013, a TV series based on the Hindu epic the Mahabharata.
- Barry Allen from The Flash (2014).
- Chapter 21 has a cameo from Dinah Drake where she gets killed by Jason Voorhees. Trish Jarvis also cameos, as do a Licker and a Xenomorph.
- Voolvif Monn has a cameo in Chapter 23, as do some other Jedi.
- An'ya Kuro has a brief appearance in Chapter 24.
- In the same chapter, there are some breach cameos when Iris West goes through a breach:
- Legolas Greenleaf from The Lord of the Rings.
- Terra Branford from Final Fantasy VI.
- Eric Draven from The Crow (1994).
- Talion from Middle-earth: Shadow of Mordor/Middle-earth: Shadow of War.
- Oliver Queen from Smallville.
- Chapter 26 has a cameo from Officer Martinez, and he ends up being killed by Freddy Krueger.
- Chapter 27 has cameos by Lord Glorfindel, Elladan and Elrohir. The Stan Lee cameo from Avengers: Age of Ultron happens here as well.
- In Chapter 28, an Earth-1 Superman/Clark Kent has a cameo, and he saves Sandra Hawke and Connor Hawke from being run down by a truck.
- Chapter 29 has various cameos on the homeworlds of some of the Young Legends, those being Katara, Sokka, Appa and Momo, Chiron and Mr. D, and Norse Kratos and Mimir.
- At one point in the chapter, Steve gives a speech to Ultron, and as he talks, various superheroes are shown stopping the nukes Ultron sent out, those being Captain Britain/Brian Braddock, Doctor Voodoo/Jericho Drumm, Aurora/Jeanne-Marie Beaubier and Northstar/Jean-Paul Beaubier and Ghost Rider/Johnny Blaze.
- Chapter 30 has breach cameos when Bart Allen runs through a breach:
- The Teen Titans from Teen Titans (2003).
- Noctis Lucis Caelum from Final Fantasy XV.
- Clive Rosfield from Final Fantasy XVI.
- Lightning from Final Fantasy XIII.
- Tidus from Final Fantasy X.
- Zidane Tribal from Final Fantasy IX.
- Squall Leonhart from Final Fantasy VIII.
- Yozora from the Verum Rex video game in Kingdom Hearts III.
- Ichigo Kurosaki from Bleach.
- Jill Valentine from Resident Evil.
- Eobard Thawne/Professor Zoom from DC Animated Movie Universe.
- There are more breach cameos when Ash Williams ends up going through a breach:
- The X-Men from Wolverine and the X-Men (2009).
- A version of DCEU Batman/Bruce Wayne from DC Extended Universe.
- John Constantine from Constantine (2005).
- The Punisher/Frank Castle from The Punisher (2004).
- The Clown from The Cabin in the Woods.
