When K.O. is transported to a mysterious destroyed city, he teams up with Garnet, Ben, and Raven to escape.
- All Your Powers Combined: When Ben gets his powers back, the Omnitrix allows him to transform into EVERY single Cartoon Network hero, making him strong enough to finish Strike with a Megaton Punch. Heroes featured, in order...
- Art Shift:
- Ben and Raven are drawn and animated more in the style of OK K.O.! rather than that of their respective home series. Averted with Garnet, who's animated nearly the same as she is in Steven Universe thanks to the episode's lead animator having previously worked on that production.
- Moxy is drawn and animated in 2D instead of in CGI.
- The Cameo: Characters from pretty much every show produced by Cartoon Network make an appearance. note
- Canon Welding: CN City, which this episode is heavily implied to take place in, already featured this idea, but this one adds a few new shows to the concept, including ones that had never properly had been in the setting, with both Ilana and Octus's presence suggesting that they were part of the city.
- Crossover: Between OK K.O.! Let's Be Heroes, Steven Universe, Ben 10 (2016), and Teen Titans Go!, along with many other Cartoon Network properties and CN City.
- Cultural Cross-Reference: Among the myriads of Cartoon Network characters who make cameos here is the main character of Jorel's Brother, which is a Brazilian CN original series and airs exclusively in the South America region.
- Early-Bird Cameo:
- Kelsey, Mortimer, and Hedgehog's shows were still in development and had yet to premiere while this episode was being produced, meaning their appearances here were supposed to be a little taste of their shows of origin. By the time "Crossover Nexus" actually premiered, however, their home shows had been airing for a few months.
- Valentino and One-One show appear in the foreground and background, respectively, months before their shows began airing.
- Mao Mao's show wasn't even announced when the episode aired, leaving many viewers wondering who his statue was supposed to be for ages until it finally debuted in 2019.
- Fake Crossover: As far as the Steven Universe lore is concerned, Garnet's appearance here isn't canon, but the information that Garnet's glasses help with her Future Vision is. They're also prescription.
- Fantasy Keepsake: After K.O. crosses the portal to his dimension, he wakes up on the floor of the Bodega. He thinks he dreamed it all, but then the POW card Garnet made him falls out of his pocket.
- Fun with Acronyms: "Crossover Nexus", in addition to being an acute name for the episode, shares its initials with Cartoon Network, something the title card for the episode even acknowledges.
- Generic Doomsday Villain: Strike, the antagonist of the crossover, doesn't seem to have any really good reason for destroying CN City or defeating the various other heroes. Raven even mocks him for it.
- Goggles Do Something Unusual: Garnet's glasses not only help her Future Vision, but are also prescription.
- Irony: A brief one. All of the striked characters are referred to as "heroes", however Black Hat is among them. Anyone familiar with his show of origin knows he is anything but heroic, and even prides himself on his villainy.
- Lampshade Hanging:
- When K.O. asks why Strike would do something so terrible, Raven replies that he's "like pure evil or whatever", referencing how he's nothing more than a Generic Doomsday Villain that the heroes have to beat.
- Robot Jones' only line in the episode is a reference to both his show's title and how said show fell into complete obscurity during its' run.
"This is what happened to me!"
- Loose Canon: While this isn't canon to her home series's continuity-heavy timeline, the details gleaned from Garnet's design and introduction would place it sometime during seasons four and five, prior to Ruby and Sapphire's wedding. This is evident by Pearl and Amethyst having the upgrades they received from Bismuth, Amethyst sporting the third version of her outfit (albeit miscolored with those of her second), and Garnet not having her wedding rings.
- Medium Awareness: Every major character is introduced with Boss Subtitles, but Raven objects to hers calling her a "magician". It then changes to "half-Azarathian, half-demon sorceress", which she finds more acceptable.
- Morality Dial: Before using Strike's weapon to restore the heroes' powers, K.O. first flips the switch on the side from "destroy" to "create".
- Mythology Gag:
- This special is oozing with references from Cartoon Network's history that it's hard to list them all. Here's a handy-dandy video.
- Ben transforming into several heroes while delivering the final blow to Strike is a reference to the Series Finale of Ben 10: Omniverse, in which Ben did a similar thing with his aliens.
- Robot Jones has a Synthetic Voice Actor here, like he did in the original run of his show's first season before they were redubbed with a human voice actor due to Executive Meddling.
- Double D being one of the heroes that Ben transforms into while delivering the final blow to Strike is a reference to an episode where he punched someone out of anger, causing people to see him as a bully and him viewing himself as a horrible person out of guilt.
- The pose Garnet assumes after introducing herself is very similar to her pose after she reforms in "Reunited".
- The show's creator named Ben's punch against Strike the "Cartoon Network Punch Time Explosion", a reference to the game of the same name.
- Non-Standard Character Design: Unlike the four heroes, the various cameo characters are all drawn in their series' respective artstyles, albeit with a number of them using stock art.
- Off-Model: In the other Crystal Gems' cameo, Amethyst has her Season 3 outfit with the color scheme of her Season 2 one, while Pearl's star is miscolored and her sash ribbon is missing.
- Original Generation: The main villain of the special, Strike, who isn't from the four shows being crossed over or any of the series that got a cameo.
- Sequel Hook: Before Garnet leaves through her portal, K.O. asks if he'll ever see her again, to which she replies with a smile and "I don't know", implying either a future sequel to "Crossover Nexus" or a proper OK K.O.!/Steven Universe crossover.
- Shapeshifter Mode Lock: After Ben turns into Four Arms, Strike takes his Omnitrix, which leaves him stuck in that form until he gets it back.
- She's Got Legs: A small reference to a mini-recurring gag from Teen Titans Go; Raven actually carries Four-Arms and Garnet (with K.O. on top of her head) with her legs, with Raven even saying that they're super strong.
- Taken for Granite: After taking their powers, Strike turns the heroes he defeats to stone. Raven cast a spell at the last second to avoid it, though she was still pinned to the wall until Garnet got her out.
- Transformation Is a Free Action: Mercilessly lampshaded, as no one attacks Strike while he powers up, though K.O. gets the idea to steal Strike's pen-laser and get back the others' powers.
Strike: Now, to start my incredibly long, uninterruptible power up sequence!
- Theme Music Powerup: A remixed version of the Cartoon Cartoons theme tune plays while Ben transforms and deals the final hit to Strike.
- Title Drop: Garnet says the show's title after putting K.O. on her shoulder, right before they fight Strike.
Garnet: OK, K.O.. Let's be heroes.
- The Worf Effect: Strike has defeated heroes from nearly every Cartoon Network show up to and beyond this point (as a few shows which hadn't premiered yet are also represented), which makes him look very powerful.