About
Train MADs, known in Japan as The Series of Heavy Stopover (大変な途中下車シリーズ), is a series of MADs featuring numerous Japanese trains as the main subject, which are made by reusing announcements in both trains and at stations.
Popularity
Japan has a complex railway system, as well as so many railway companies all over the country. Therefore, there are many kinds of announcements in each company and their train lines. Railways and trains are one of the major hobbies in Japan and there are many rail fans. And because of that, several train simulators (such as Densha De Go!) just driving a train as directed gains popularity, which is one of the reasons why its market is huge in Japan. Therefore, the amount of videos are so many. But none of them has given impact to outside of Japan’s popular video-sharing website Nico Nico Douga (NND). This meme even has a well-written Wikia website.
Spread
According to the Wikia, the trigger is this: JR EAST announced the precious thing (beta) (left). It was uploaded to NND on July 13th, 2007. And its complete version (right) was posted on July 21st, 2007. Of course, it’s a derivative of the Touhou song “Marisa stole the precious thing”, the most popular musical resource in the earliest days of MAD video phenomena on NND.