- Acclaimed Flop: The first game sold poorly upon release due to being overshadowed by other games like Jak and Daxter and Ratchet & Clank. The game increased in sales the following year of the game's release, especially overseas.
- Dummied Out: In addition to the normal stages' developer commentaries, dev commentary tracks exist for every minigame stage in the game and every stage of the last world except for the final boss's level, but since none of those levels have Master Thief Sprints, it's impossible to hear their dev commentaries without hacking.
- DVD Commentary: Level commentary, actually, for those who beat the speed runs in the first game.
- What Could Have Been:
- Early designs of Sly were more chunky and his clothes varied, with one wearing less clothing◊ and another having a turtle neck design◊. He was also much younger at one point in development. His original name was going to be JT, but this was changed early in development. Sly originally had a Jersey-style voice before becoming a more classic suave-voiced thief.
- Sly originally had a cane with multiple unique functions. At least some of these functions included creating a sort of water cone that could reveal a hidden maze by spraying it, freezing crabs to make them crust over and die, and freezing fish into blocks of ice to create walkways.
- Carmelita Fox originally had a different, less revealing design that was only found in very early demos of the first game. Her voice was more Hispanic-accented than the final, and her name was originally Chase Montoya Fox. She was also going to shoot bullets or small missile-like rockets but it was changed to a shock pistol to ensure an E rating.
- Bentley's voice was more stereotypically nerdy than the final.
- Murray was going to be bisexual, but it was scrapped because he reminded the testers of Barney the Dinosaur. Regardless, it would have been inappropriate for a kids' game at that time, though some elements of this behavior appear in the fourth game.
- Another early concept for Murray was a Rambo-esque character with machine guns. The only remainder of this idea is the turret levels in the final game.
- According to some audio dialogue in an early E3 preview alpha build (from what would become "Murray's Big Gamble"), Murray was originally more dimwitted.
- In some concept art there were two meerkat like characters named Zig and Zag. In early versions of the game, mainly in demos, one of them is seen in treasure chests that act as checkpoints. In a podcast with Kevin Miller, he stated they were news reporters.
- Originally the Fiendish Five were somewhat different.
- Muggshot was originally a cowboy-inspired bulldog instead of a gangster.
- The Panda King was more Han-inspired than sumo wrestling and Kung-Fu inspired.
- Clockwerk originally started out as a thousand-year-old stone gargoyle before becoming a mechanical owl.
- The original currency consisted of both coins and dancing cash bundles. The cash bundles were removed for localization reasons.
- Originally Sly's eyes were always meant to be seen, even in the dark, but it wasn't implemented due to technical issues. However, this made it into the sequels.
- The game originally had other Thievius Raccoonus page abilities that were planned (such as "Teleportation") but were never implemented.
- Originally the game's power-ups were going to correlate to the Fiendish Five gang members, which was possibly scrapped when they changed the member's level and character themes. This is evident in the first level, which was going to have the Panda King instead of Sir Raleigh. Sly would learn The Ninja Spire Jump from the Panda King's section of the Thievius Raccoonus instead of the turret addition to the Cooper Gang's van, which would be more fitting for a Gadgeteer Genius like Raleigh.
- Sir Raleigh's level was initially going to be completely underwater, with the Cooper Gang needing a submarine-like watercraft to get around. Also, the level "Into the Machine" was going to have a mini-boss fight with an octopus but it was cut out.
- Raleigh's boss fight was much different in concept art, with him using a mechanical crab with razor blade claws.
- Muggshot's location was originally a junkyard in Texas, but this was scrapped due to the level having too much visual clutter, making it nearly unplayable according to playtesters.
- In the final stage, Clockwerk's death ray was originally a giant mechanical lighthouse. Other ideas included a series of windmills and a volcano tube.
- An early concept for the Cooper Van would have had it transform into an RV as a secret hideout for when you visit different stages. At one point the characters would have driven other vehicles, such as a snowmobile and a normal car, showing that the Cooper Van was not yet conceived.
- Similar to Crash and Spyro, Sly would have been redesigned for a Younger Japanese Audience according to this concept art.
Trivia / Sly Cooper and the Thievius Raccoonus