Canon Discontinuity: For Epic themselves and many people, Unreal Tournament 2003 never existed, and said game is a beta version of Unreal Tournament 2004 instead. It gets weird storyline-wise, since the events of that game (most notably Gorge being the current Champion) still technically happened.
Unreal Championship 1 and 2 were also erased from the timeline.
2003 has three unused menu themes as well as "Level 2"note The menu theme for Unreal Championship.
2004 has two unused menu themesnote The third one was reused for the single-player ladder intro cutscene, the themes "Hell" and "Level 9"note which in 2003 were the theme songs for the maps DM-Curse3 and CTF-DE-LavaGiant2; the former was replaced by DM-Curse4 (which uses "Morpheus 3" as BGM) and the latter was cut without any replacement, and "Onslaught 06". As for "Level 2", it found use as the BGM for the map DOM-Renascent.
Official Fan-Submitted Content: Most of the content of the Bonus Pack 2 is composed by entries of the "Make Something Unreal Contest". CTF-CBP2-Pistola won the Best Map award, while all of the Assault maps except AS-BP2-SubRosa were placed between 1º and 5º places in the Best Assault Map category.
Updated Re-release: It should be noted that all of the upgrades and features available in the updated releases are also available as free downloads to owners of the original game. 2004' serves as a notable exception, where instead owners of 2003 were able to receive a discount on their purchase of the game.
Unreal Tournament 2004 towards Unreal Tournament 2003: UT2003 + its two Bonus Packs + extra content.
2004 itself has the Editor's Choice Edition, which included several mods and the Editor's Choice Edition Bonus Pack, which was later released as another free Bonus Pack.
Working Title: Unreal Tournament 2003 started it's development as Unreal Tournament 2. It was changed by Digital Extremes in order to emphasize the sport side of the franchise.