In Crash Bandicoot 4: It's About Time, the relics only appear as 2D images. However, complete 3D models can be found for all of them inside the game, including three variants of the N. Sanely Perfect relic that seem to be tiered (one being a skull, another being a skull with crossbones, and the last being a skull with crossbones; wings; horns; and a more menacing face which is closer to the final N. Sanely Perfect Relic aside from the wings), all with their own animations.

Crash Team Rumble had been teased officially as far back as Crash Bandicoot 4: It's About Time's release date in 2020 - first in It's About Time! where, after 106% completing the game, the player could return to the start of the game and spin Crash's TV multiple times to show a mysterious Wumpa Fruit symbol. This would shortly be followed by a cross promotional video for Uncharted, where the symbol could be seen again on a banner with the words "Wumpa League".

Later in 2021, a Game Designers Conference talk with Toys for Bob studio head Paul Yan would show two hints towards the game's existence: one on a graphic made to show the game's goals with a set of green "this game is..." post-it notes (such as "new vehicles" or "cartoony animation" and red "this game isn't..." post-it notes (such as "beat 'em up" and "open world") with Wumpa League put in the middle as a yellow "might be", obscured by another note; and a second where the screen very briefly flashes to concept art of "Wumpa League". Crash content creators and game journalists would soon receive Wumpa Fruit-shaped pinatas with the Wumpa League branding and colors, which was then followed by a set of meme tweets on the Crash Twitter account relating to Wumpa Fruit, one of which being a play on the It's Always Sunny in Philadelphia Pepe Silvia conspiracy board meme. Toys for Bob would later release a Crash anniversary celebration video showing the Wumpa League logo again along with a Gem variant. The Wumpa League logos would show once more in the background of a PlayStation crossover commercial. The final tease of 2021 would be in a Christmas package sent to the press which had the Gem sticker placed on the side of the box.

In 2022, the hints started rolling in again on St. Patrick's Day, when Toys for Bob posted a piece of concept art for Crash 4 edited to have four-leaf clovers littered throughout, asking players to find the seasonal hidden objects. However, the Wumpa League symbol was hidden alongside the clovers. Later, the press and Crash fandom would recieve another package, this time an Aku-Aku-branded pizza box promoting Crash 4's release on Steam, with "HUNGRY FOR MORE? TRY OUR NEW WUMPA PIZZA FOR $12.08!" written on the side - the price translating into the date of August 12, which was the date of the Game Awards, which is ultimately where Crash Team Rumble would be revealed.

In the Flashback Tape "Bandicoot vs. Wombat Eval", Cortex compares the results of preliminary tests deciding on if he should use a bandicoot or a wombat for future experiments to turn him into a general. Near the end of the game during the "Toxic Tunnels" stage, he exclaims had he chosen a wombat rather than a bandicoot, "this could have all been different". This plot point is a nod to Crash's early incarnation Willy the Wombat.

In the Flashback Tape "The Gauntlet", Cortex will say "Maybe next time I'll try a hedgehog…or a bobcat…or a gecko". These are references to Sonic the Hedgehog, Bubsy the Bobcat, and Gex the Gecko, all of which were wisecracking anthropomorphic characters from 1990s platformers, much like Crash.

This game features the first instances of swearing in the Crash Bandicoot franchise:
•Dingodile utters “bastard”, “buggers”, and “bollocks”
•Tawna at one point says “Give him hell!”
•Coco in the 100% ending is referred to as “Kickass Coco”

Despite Crash Bandicoot 4: It's About Time's intense difficulty, the game's producer Louis Studdert was concerned before the game's launch that Toys for Bob may have made it too easy.

During the level "A Hole in Space", if you collect all 18 Bumpa Berries while riding the grind rail, you will be rewarded with a visual effect of a group of low-poly Crash Bandicoot/Coco models screaming "Woah!"/"Yeah!" respectively, while also earning the achievement "WHOA YEAH!". This is a reference to a CG animation created by Chris Patstone that was based on a video voice acted by animator Chris O'Neill, which became a meme in 2017. The in-game reference uses individual frames of the same model of Crash featured in the original video, but O'Neill's voice is dubbed over. The Coco model is used from a pre-existing variant on the meme created by animator Zellphie.