Deleted Scene: The disc for Adventures contains several voice clips absent from the game itself which indicate that Krystal originally had a more prominent role and would have teamed up with Fox to help him navigate through the final dungeon (in the retail version, she is playable only for a few minutes at the beginning of the game, imprisoned, and then released just before the end). The romantic subplot between the two is also slightly expanded upon; after Andross is defeated, Fox asks Krystal to join Star Fox, and she agrees on the condition that he kiss her first. Samples and transcriptions of the deleted audio can be found here.
Executive Meddling: At the time of its development, Rare's owners had begun openly trying to find a new buyer for their company. In late 2000 they had held meetings with both Activision and Microsoft. The move to include Nintendo owned characters into Dinosaur Planet meant that once Microsoft acquired Rare in 2002, the game was still a Star Fox instalment and Rare had no rights to any of the characters.
The original Dinosaur Planet concept seemed interesting in its early stages. How the game would have fit together without shoehorning the Star Fox universe into it will forever be a mystery.
Sabre. Poor, poor Sabre never got to see the light of day. All because of Fox McCloud and Nintendo.
Some early material from the original game concept such as screens, gameplay and trailers, can seen here.
The game was originally intended to be a Diddy Kong Racing sequel with the main character being Timber as shown in the files for Sabre's character. If they hadn't replaced Timber with Saber, Nintendo might have shoehorned DK into the game instead with Wizpig taking Andross's place (in fact that was the original intention to begin with).
The game was originally going to be on the Nintendo 64 and, based on the cartridge size (512 Megabits), would've probably been the most ambitious game yet on the system. Eventually, it was decided that the game was a little too demanding for the system's limited hardware, so it was released on the GameCube instead.