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In all the racing levels of Crash Bandicoot 3: Warped, if you look closely at the registration plate of the opponents' car, it reads "96-17".

These 2 numbers are references to the years of the release of the original Crash Bandicoot in "1996", and the remake trilogy in "2017".
Contributed by ProtoSnake
Coco's laptop and phone displays stickers featuring the "Naughty Dog" and "Vicarious Visions" logos.
Contributed by ProtoSnake
While waiting for one of Coco's phone idle animations, her phone will start to spark and then she'll toss it away right before it explodes. You can also break any boxes, even kill yourself if TNT or Nitro are caught in her phone's explosion.
Contributed by ProtoSnake
Inside Crash's home during the opening and ending scene of "Crash Bandicoot 3: Warped", you can see picture frames of "Nathan Drake" from the Uncharted 4: A Thief's End and "Tawna Bandicoot" from the first game.
Contributed by ProtoSnake
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During one of Coco's idle animations, you can see the Crash Bandicoot sub-reddit on her laptop.
Contributed by ProtoSnake
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During the intro cutscene of "Crash Bandicoot 2: Cortex Strikes Back", Coco Bandicoot is watching a cutscene of Nate and Elena from Uncharted 4: A Thief's End on her laptop, playing the original Crash Bandicoot on the original PlayStation.
Contributed by ProtoSnake
During the intro cutscene of Crash Bandicoot 2: Cortex Strikes Back, Naughty Dog's paw icon can be seen on a passing asteroid.
Contributed by ProtoSnake
In the boss fight with Tiny in Crash Bandicoot Warped, if you stand in the top left corner of the arena as the lions are coming out, the audience will start throwing cheese at you. A reference to a glitch found in the original version of the game.
Contributed by gamemaster1991