As put so very well by The Daily What, "Something worth keeping in mind while watching this short clip from Japanese erotic horror flick The Big Tits Dragon: Hot Spring Zombies Vs. Strippers: You are awake and this is real."
An explanation, as offered by random strangers on the internet: Its a parody of the original Korean pop song by changing the Japanese title of the song. The title is "Girls Generation" which in Japanese is shojo-jidai, which they've changed to showa-jidai - meaning the "Showa Generation" (Showa period was from 1926 to 1989).They also did a play on the song title "Gee," by changing it to the Chinese character for an elderly man (爺), which is also read the same ("ji").