This script allows you incorporate characters from GTA V into GTA IV. It lets you switch between Niko, Luis and Johnny in your GTA IV games. Note that this script is under development and still has bugs.
Installation
To use the script, you need to install and configure OpenIV and ScriptHook. A complete tutorial on the script developer's site is available here. It also includes a download link for ScriptHook.
Download GTA V style in GTA IV - Char switch in Softonic