Beta Leftovers are files which were intended to appear in the final release of the game, but they were scrapped due to time constraints or otherwise unknown purposes.
The following is a list of Beta Leftovers in Grand Theft Auto IV.
In the game's files, one specific file can be found called "space_hud.wtd" When loaded, it shows a space ship, HUD, and other things. This gives clues that there was a space mission in GTA IV or its episodes. The other possibility is that there was once a minigame similar to They Crawled from Uranus from Grand Theft Auto: San Andreas.
In the files, another strange file can be found called "zombie.wtd" It shows some strange things such as blood, bullets and guns, giving clues that there was a Zombie minigame. It is also being further proven by the fact, that the Z Ressurection logo is in the files.