I haven't found any information on this on the internet, so here it goes:

To prevent the intro movies from playing locate your game's installation folder, usually "GOG Games\Crusader Kings Complete". There is a folder "avi", enter it. Now rename the file "binkplay.exe" to something else, like "_binkplay.exe", it doesn't really matter as long as the name is different.

The intro movies were causing me problems, that's why i was looking for a way to disabled them in the first place. From what I see there aren't any other movies to play, so this should be safe.