4. Bill & Ted Save the Soul of Metal
Bill and Ted decide to take the time machine phone booth back in time somewhere for a vacation with the babes, and then on the way out, accidentally leave an iPod behind. The iPod, containing Wyld Stallyns music, is then picked up by a young not-yet-in-power Hitler/Stalin/Mussolini/bad historical dude who tries to use it for his own evil deeds, creating a butterfly effect, an alternate timeline in which metal and rock really are the Devils music. Bill and Ted must then venture back in time to prevent rock from becoming a force for evil. Bill and Ted fighting Stalin and pronouncing it Stale-in seems fitting for the franchise.