Crash Bandicoot
Crash Bandicoot - Did You Know Gaming? Feat. Caddicarus
According to a later version of the "Project Wombat" developer bible for Crash Bandicoot (this version was given to a fan by the game's producer David Siller in 2015; an earlier version of it was officially published in 2018 in the book "The Crash Bandicoot Files: How Willy the Wombat Sparked Marsupial Mania"), Dr. Neo Cortex's backstory describes how he and Dr. Nitrus Brio when they were younger destroyed their high school by tampering with the physics department's test nuclear power plant. Afterwards, they traveled the world looking for a new home, but no matter where they went they were ridiculed and ostracized, and it is noted that soon after they left a location, that place was then met with "violent explosions and catastrophes". This culminates in one last account where the pair left the city of Chernobyl, drawing the attention of various international law organizations who connected the dots to their past incidents and soon added Cortex and Brio to the international most-wanted list. Feeling the heat, they finally settled down far away from humanity on the Australian island that he would soon name Cortex Island. This backstory heavily implies that Cortex and Brio were responsible for the real-life 1986 disaster at the Chernobyl Nuclear Power Plant in the Soviet Union.
Contributed by MehDeletingLater
In the first three games, a glitch can be performed when bouncing on multiple enemies consecutively. Normally, by bouncing on 5 enemies in a row, you get an extra Life in addition to 3 Wumpas from the previous 3 enemies in that combo. However, the bonuses that come from bouncing combos go further beyond that into triple-digit combos as a result of there being no set combo limit. This means if performed correctly, triple-digit combos can overflow the item table to give key items that you are not intended to get through them including Tokens, Crystals, Gems, Sapphires, Relics and Powers.

This can be achieved through tool assistance or through human play by building up the bounce combo on a respawning enemy or more ideally an Iron Arrow Crate, and then continuing the combo on enemies to start reaping these items. Preserving a bounce combo can be done by spinning and crouching right before hitting the ground, as the combo count is lost when Crash enters the standing or walking animations.

The attached image features a list of items that can be earned through this glitch, as well as the requirements for glitched higher percentage runs of each game, created by speedrunners dass and ThaRixer, the latter of whom originally utilized the glitch to dramatically lower the speedrun record of Crash Bandicoot 2: Cortex Strikes Back in 2012.
Contributed by MehDeletingLater
Originally, Nitros Oxide was going to be a human scientist obsessed with speed. This tied into an early plot in which Oxide planned to make the world spin faster and faster until the end of time using a machine called the "X Device". The idea was dropped early on in development and Oxide became an alien set on conquering Earth.
Contributed by Doctor Ink
In 2014, a fossil from an extinct species of peramelemorphia (the order which includes bandicoots and bilbies) was officially described and given the scientific name 'Crash bandicoot'. The scientists responsible state in their report that it was named after the video game character, and also in reference to how it was the start of a new lineage of modern bandicoots that 'crashed' through to dominate the ecosystem.
Contributed by HootingLance
A kart racer was planned to be released along side the cancelled "Crash Landed", the game was being lead by High Impact Games, a studio mostly comprised of former Naughty Dog and Insomniac Games employees. The game would have featured a number of returning characters, including Crash Bandicoot, Dingodile, and the long awaited return of Polar. A new character know simply as "Land Shark" was to be introduced. High Impact Games decided to introduce a dynamic kart modding system, in which the player could equip their character's kart with a number of crazy gadgets, including "Crab Tires" for good speed on sand, "Octopus Tires" to suction onto vertical surfaces, "Pig Engine" to belch their way to first place, and many more wacky gadgets. Unfortunately when Activision made the call to cancel "Crash Landed", the same went for this game.
Contributed by SpaceChimp
Naughty Dog decided that the original Crash Bandicoot games would be exclusively released on the PlayStation due to the Saturn not being strong enough for their desires, and they considered developing for the Nintendo 64 would be far too expensive to publish games on due to their cartridge based system.
Contributed by GamerBen144
Toy company Resaurus Toys produced action figures based on the first three games from 1998-2000. Only two series were produced, likely because of their fragility. A third series was planned, but never made it past concept art. It would have included an arctic Crash variant, Koala Kong, Papu-Papu, N. Brio, Pinstripe, and Ripper Roo.
Contributed by SpaceChimp
A cancelled game, called "Crash Landed", was in development by Radical Entertainment. It appears it would have been a reboot of the series. The plot was based around Crash trying to save primitive bandicoots (or 'bandicutes' as they were called in the concept art) from Neo Cortex. Dingodile would have served as a secondary antagonist.

The game was cancelled in 2010 after two years of development. After Activision acquired the rights to publish the franchise, they decided to lay off the entire Radical Entertainment studio behind Crash Landed. Activision's decision to not pass the project to a different studio suddenly halted its progress forever.
Contributed by SpaceChimp
The character Nina Cortex was created by Traveller's Tales Oxford Studios for Crash Nitro Kart. However, Vicarious Visions was assigned to develop the game instead, so TT-Oxford planned to debut Nina in Twinsanity. However, when screenshots of Crash Fusion (developed by Vicarious Visions) revealed that Nina would appear in that game, TT-Oxford was shocked, as they had not been asked or even notified that their work would be used in another game, which would release even before their own.
Contributed by SpaceChimp
After Crash Tag Team Racing was transferred to Radical Entertainment, Traveller's Tales Oxford began working on their own game starring Cortex. They put forth several proposals, but were not given the go-ahead to develop any of them.

Prospective titles were "Cortex Chaos" and "The All-New Cortex Show", and gameplay may have involved him ordering clones or robots around, similar to Pikmin. Cortex would have been kicked out of the Evil Scientist league for "fraternizing" with Crash during the events of Twinsanity, and the other evil doctors, led by N. Tropy, would have been the primary antagonists.
Contributed by Spherix
The concept of Trash Bandicoot (now known as Fake Crash) came from some cheap looking knock off Crash Bandicoot dolls. These dolls had huge eye brows and a giant overbite.
Contributed by gamemaster1991
According to Andy Gavin, the creator of Crash Bandicoot, Dr. Neo Cortex is based on Brain from Pinky and the Brain.

"I remember it clearly. The four of us were eating at this mediocre Italian near Universal and I had this idea of an evil genius villain with a big head. Obviously brainy cartoon villains have big heads. He was all about his attitude and his minions. Video games need lots of minions. Jason had become very fond of Pinky and the Brain and we imagined a more malevolent Brain with minions like the weasels in Who Framed Roger Rabbit. A villain, all full of himself, unable to conceive of ever doing anything the simple way, but constantly (in his eyes) betrayed by the incompetence of his henchmen.

I put on my silly villain voice and intoned, "If you had three neurons between you, you couldn't make a triangle!" With this attitude, his name, Doctor Neo Cortex, popped instantly into our heads."
Contributed by Berry
Crash was originally named Willie the Wombat and was created as a much bulkier character. During production of the first game, the marketing director of Universal Interactive Studios insisted that Crash be named "Wez", "Wuzzles" or "Wizzy the Wombat". Crash was given his final name due to his tendency to smash crates.
Contributed by AussieYak
According to Naughty Dog, Dr. Neo Cortex uses Rogaine, but only on the sides of his head.
Contributed by Ripper Roo