The first game in which Lex Lang replaced Clancy Brown as the voice of Dr. Neo Cortex. He became the regular voice of Cortex from there.
In an interesting note, this is the last game to feature any English cast members from the Naughty Dog games. Mel Winkler voiced Aku Aku for the last time in this title before being replaced by Greg Eagles in Crash of the Titans, while Michael Ensign, who had reprised his role as Dr. Nefarious Tropy in Nitro Kart, returned for Tropy's two scenes in this game. None of the original cast have returned since, including the N. Sane Trilogy.
Troubled Production: An astounding example of this. There's loads of missing content, unused ideas, and whole models that ended up getting thrown out. As a result, the game is pitifully unfinished, even if it's pretty fun.
The game was in development around the same time as the original LEGO Star Wars, and most of its budget was being funneled to that instead, seeing as a license like Star Wars would be a much more profitable choice.
Collecting yellow gems unlocks "unseen extras" which apparently feature ideas and concepts that never made it into the final version. This is lampshaded by Cortex once: "We were going to visit two dimensions, but... we ran out of time."
Several hours worth of content was removed from the game, including several returning characters, new levels, and a Villain Song for Dr. Cortex entitled "Take a Walk Inside My Brains". Two members of the development team released a great deal of information on these removed items, which can be viewed here.
At least two direct sequels were also planned, but never made it past early planning due to Traveler's Tales' Oxford unit shutting down.
There were plans for a Gamecube port, but due to difficulties with porting the engine, the port was scrapped