If the player completes the whole trilogy in 100%, they'll be able to see "Fake Crash" in some of the levels. This includes:

"Crash Bandicoot"
N. Sanity Beach: At the left side of the stone stairs.
Heavy Machinery: In one of the pipes near a platform that takes Crash down to a different path.

"Crash Bandicoot 2: Cortex Strikes Back"
The Pits: At the left side of the path, near the first big mushroom, right after the split path ends.
Crash Crush: On the left side of the path while Crash is getting chased by a boulder.
Hang Eight: At the end of the Blue Gem route, on an un-reachable platform with two Venus Fly Trap enemies.
Ruination: At the right side of the first platforms moving in circle.
Cold Hard Crash: In the first ice mirror in the death route.
Rock It: At the right side of space, in the first glass room.
Totally Fly: Between a tree and a tiki statue on the left.

"Crash Bandicoot 3: Warped"
Toad Village: On the lawn, enclosed in a fence, of the 3rd house on the right. There is a pond in front of the house where Crash can walk on.
Makin' Waves: On a small island with grass, and a palm tree, at the end of the level, on the right.
Hog Ride: Seen dancing on the left side of the road. He is in between the gas station and the Cortex sign, near the two ramps right next to each other.
Area 51?: Left side of the road near a tall cactus, on a left turn.
Future Tense: Near the end of the death route, on a building to the right.